Our most recent experiments on the light-induced drift effect are reviewed and discussed. Results are presented on the isotope separation of Rubidium, for the first time experimentally demonstrated upon saturated vapor conditions. A new manifestation of the light-induced drift, known as "white light induced drift", has been experimentally demonstrated by using a laser with a particular cavity configuration and special-spectral characteristics. Finally the production of vapor jets by light controlled diffusion is reported and its possible application discussed.

The paper reviews various schemes of lasing without population inversion with particular emphasis on these which seem to be most promising from the practical point of view. It is shown that in some cases one can attribute the lasing to the population inversion in an appropriate reference frame.

We discuss the application of the multicomponent Wigner function to the study of mechanical forces acting on atoms in a laser beam.

The high-resolution infrared band spectra of the v1, v2, and V4 fundamentals of methylisocyanide have been measured with an interferometric spectrometer at an unapodized resolution of 0.004 cm1. The spectra, yielding fully J and K-resolved transitions, are analyzed and fit to spectroscopic constants. In each case some of the major perturbations were identified.

Electronic emission bands of In2 are generated (a) in a microwave discharge in a quartz cell containing the metal plus a low pressure of Ar or Ne and (b) by radiative combination of In atoms excited to the 6SS1fl state with In atoms in the ground (52P1) state. In (a) a band progression to high energies was observed commencing at 25 730 cm1 which can be fit by moelcular constants of ue 105.3 cm1, COXe 26.2 cm1, and De 212 cm1. In (b) strong, unresolved, overlaped band features were observed in the 380 nm wavelength region (25 500 cm1 to 27 000 cm ) and a weaker, broad feature at 375 cm1 (28 300 cm1 to 30 000 cm1).

This work illustrates the temporal analysis we have done on the fluorescence signals originating from levels with pecularly different characteristics populated either via Energy Pooling Collision (EPC) or via Energy Pooling Ionization (EPI). The fluorescence from the first excited level (S ia) gives informations about the limited radiation trapping due the fine structure of the ground state l/2 3/2 the ones from the 1 1P and 5D levels allow to discriminate between the different population mechanism, EPC and EPI respectively. The cross sections for the two different processes may also be obtained.

Creation of a coberent two-phonon overtone state ofa lattice mode in crystals in the process of parametric excitation by bihaiineoic optical field is presented The dynamic of the system is described by the set of three differential auations with modulated in time parameters. It is shown that in the presented system the intrinsic optical bistability occurs.

The interest in nonlinear liqht reflection phenomena is caused by the fact that they can give a unique information about crystals' surface properties In this work we have used the boundary conditions on the surface of nonlinear media with space dispersion (SD) obtained in. We have considered phenomenologically polarization effects due to interaction of the two arbitrarily polarized waves durinq both propagation and reflection from crystals of cubic, hexagonal and tetraqonal crystal systems (the incident angles of light are supposed equal to zero, and the crystal optical axis to be perpendicular to the boundary). 10 both cases for media with weak gyrotropy four mechanisms of nonlinear optical rotation (NLOR) and deformation (NLOD) of polarization ellipses have been determined. It has been made )fl a first approximation with respect to the parameter of SD Jd/. (here ci is a characteristic length of spatial non-locality ot response, ?*, is a wavelength). The influence of linear qyrotrop>' and dissipation on the interaction ha also been investigated. A nonlinear polarization spectroscopy scheme has been suggested. This scheme allows one to distinqush between contributions of different NLtJR and ILOD rnechansms irrespective of the crystal symmetry. The study of NLOR and NLOD effects during the interaction of two elliptically poirized waves with the medium is shown to give three or four as much spectroscopy information on the cubic nonlinearity and )ts SD as in the case of application of a plane polarized wave. Moreover the joint study of liqht polarization interaction during both reflection and propagation of waves through the crystal is most effective. This is connected with the fact that spectroscopy information received in experiments 'on reflection' and 'on propagation' is complementary to a great degree

Modifications of a natural emission line of a free atom, due to its concentrated center of mass wave-function, have been studied. The Doppler shifts, associated with the corresponding momenta distribution of the wave packet, are responsible for the shape of the emitted line. We found, that the modifications of the emission line shape do not cause any changes in the life time and the total radiation intensity.

A new method of rate constants for electron impact induced transitions between excited atomic levels determination is presented. The results for 3P→4P and 3P→5S transitions in sodium atom are in good agreement with Gryzinski's theory.

Four band systems corresponding to transitions from excited electronic triplet states of the molecular Na(3S)+Cs(5D) and/or Na(3P)+Cs(6S) state manifolds to the lowest a3E triplet state were observed under laser excitation of NaCs molecules at 476- 577nm. Emission of the bands is due to pertubations and collisional energy transfer in the upper states. The equilibrium internuclear distance in the a3E+ state re 5.6A was estimated and the lifetime of one of the excited triplet states involved in the observed transitions was found to be equal to 29.4(4.2)ns.

The low-lying triplet states of the lithium dimer are of particular interest because of their role in the predissociation of states correlating with the 22S112 +22P3a,la atomic states of Li. In this work, the fine structure of the b(1)3H state of 6Li2 is investigated using Doppler-free polarization spectroscopy. The triplet state is accessed using one of the rare singlet-triplet intercombination transitions. In such a transition only one of the triplet fine structure sublevels receives intensity through spin-orbit interaction with the A1EJ state. However, the remaining two fine structure levels can be excited by using the Zeeman interaction to mix levels of different J. Two polarization geometries were used in separate experiments to study different groups of M levels in magnetic fields up to 3 kG. An irreducible tensor derivation of the fine structure and Zeeman Hamiltonian matrix in Hund's case (b) symmetrized basis functions was used to find the electronic perturbation parameters and the spin-spin and spin-rotation fine structure constants by a fit to the Zeeman splitting pattern. In the particular case presented here (levels with high J), the spin-orbit contribution to the fine structure was too small to be accurately determined. However, the electronic singlet-triplet spin-orbit interaction could be found with high precision.

By severely reducing the number of solute molecules in the illuminated sample, the optical resonances of individual molecules can be resolved in a fluorescence excitation spectrum. Single molecule lines can be studied as a function of time and temperature: sudden jumps of their resonance frequencies are due to spectral diffusion processes. The signal from a single molecule displays specific correlations which makes time-resolved studies possible. Here, emphasis is put on photon-bunching arising from intersystem crossing (ISC). ISC rates are deduced from the observed decay rates of the correlation and are found to differ from molecule to molecule. A single molecule is a truly local probe of its environment by means of which fundamental studies of the matrix dynamics as well as nanophysics experiments may be undertaken.

Dynamic microspectroscopy systems have been developed for elucidating photophysical and photochemical processes occuring in small volumes. The first system concerns fluorescence spectroscopic measurements based on a timecorrelated single photon counting and a confocal fluorescence microscope, which makes it possible to observe the fluorescence dynamics with both picosecond time-resolution and micrometer three-dimensional space-resolution. The second system is for absorption spectroscopic measurements. Picosecond pump and probe beams are coaxially and confocally introduced into a microscope, giving the depth profile in addition to lateral information. These systems are further combined with a trapping laser which optically tweezers a single microparticle against its Brownian motion. Laser trapping thus introduces the precise time- and space-resolved measurement of particles. To analyze rise and decay curves as a function of position and wavelength, a new fast and accurate analyzing method using a convolved autoregressive model has been proposed. The computation time of this method is much shorter than that of the conventional methods. The present systems have been applied to various kinds of microparticles such as microcapsules, polymer latexes, and oil droplets.

The lowest electronic transitions of many absorbing centers in solid hosts consist of extremely narrow zero phonon lines distributed over a broad spectral range. Frequency selective modification of such inhomogeneously broadened bands has several potential applications. In very dilute samples inhomogeneous broadening provides a key for spectroscopic isolation of single absorber resonances.

Carbonyl derivatives of N,N-dimethylaniline have been investigated in polar aprotic solvents using time-resolved techniques in absorption as well as in emission. The kinetic relation between short and long wave fluorescence bands is observed. The nature of the time-resolved solvatochromic shift is discussed.

We report an application of laser spectroscopy techniques to a study of collision-induced interactions in atomic excited states. Due to pulsed dye laser excitation a considerable selective population of highly excited states of ccsium is obtained. Collision-induced transfer of excitation energy between the excited states results in modifications in time and spectral characteristics of observed atomic fluorescence. Quantitative information on the efficiency of collisional processes can be obtained from the measurements of time constants of the time-resolved fluorescence signals and/or from those of the integrated intensities of the fluorescence lines. Both possibilities are used in the present work. Perturbation of nD (n=8-14) and nS (n=1O-15) states of cesium in collisions with noble-gas atoms is investigated. The cross sections for the transfer of excitation between fine-structure substates of the nD states (J mixing) and for the nS-(n-4)F intermultiplet transfer are obtained.

Excitation spectra of CdNe and CdAr van der Waals molecules were studied in freejet expansion molecular beams crossed with a beam of exciting radiation from a pulsed dye laser. The molecules were produced as Cd atoms seeded in Ne or Ar were expanded through a nozzle and the excitation spectra were recorded by scanning the second-harmonic output of the dye laser in the immediate vicinity of the Cd(51P1 _5lS)atomic transition, in the range 2288-2290.5A for CdNe and 2288-2305.5A for CdAr. Analyses of the vibrational structures of the spectra yielded the molecular constants we ' e X and De for the D 1 states of CdNe and CdAr. Computer-modelling ofthe spectrabased on calculations ofFranckCondon factors utilizing the Morse potential produced the equilibrium internuclear separations.

We present terminal population of seven vibrational levels, v"=1-8, in Na2 supersonic beam formed by pure Sodium expansion. It was determined by the laser induced fluorescence method for source pressure x nozzle diameter product p0d=0.32, and covers 550-1550cm' energy range. The population forms a continuous, non-thermal dependence of the internal energy, and does not depend much on the partitioning of this energy between vibration and rotation. We think, that this new result is not in contradiction with observation of previous experiments, but suggests new interpretations.

In investigations of hyperfine structure (hfs) by the quantum beat method, the two-photon excitation scheme was introduc to4tta a numb of highly excited D states of some alkali metal isotopes ( K, K, Rb and Rb). In the present paper some details of the experimental technique are presented. The values of the magnetic-dipole interaction constant A and the electric-quadrupole interacion constant B, obtained in a series of experiments for the states of interest (6 D312 5/2 of 39K, 62D312 of 41K, l1,122D312 of °5Rb, lO-132D312 and 9-132D512 of 87Rb) are summarized and compared with other results concerning hfs of the D states of the same isotopes. The relatively simple method proved to be quite effective .n extending the measurements of hyperfine interaction constants to highly excited D states of alkali metal atoms.

Absorption spectrum of cadmium vapour is measured over the spectral range 300 - 326 nm with a high resolution concave grating spectrometer. Two systems of molecular bands at about 800 cm1 (A + B) and 1800 cm1 (C) from the center of the 326.1 nm Cd intercombination resonance line are observed, the latter for the first time. In order to explain the origin of these bands the temperature dependence of spectra as well as an effect of foreign gas on their intensity is measured. The results seem to indicate that the strongly structured band systems B and C are due to the excited state absorption from the bottom of one of the gerade states correlated with the 51P1+ 51S0 asymptote to a highly excited Rydberg ungerade states of the Cd2 excimer. The energy separation between the potential minima of the lower and the upper states is determined and the vibrational frequencies of the upper states involved are estimated. On the other hand, the 1 potential curve correlated with the 53P2+51S0 asymptote is deduced from the analysis of the diffuse band A which is interpreted as a satellite of the forbidden Cd line due to the 53P2 - 5'S0 transition.

An automatic interferometric method is proposed for measuring the transmission peak wavelength of monochromatic filters and their bandwidths. The fringe interference field is sampled by a standard CCD camera and processed using a PC computer. These above mentioned spectrometric parameters of filters follow from the analysis of the interfringe spacing and fringe intensity distribution ( visibility of fringes ). A known double-refracting interference microscope was used in the performed experiment.

The application of the holography methods to the interference spectroscopy make it possible to expand the field of application of the "hook" method. The method is based on the interference spectroscopy principles supplemented with the holography principles. The new holographic methods with increased sensitivity for the investigation of susceptibility spectrum (index of refraction and absorption coefficient) in the linear and nonlinear spectroscopy are described in this report.

Phonon and polariton excitation was studied in CdS and ZnSe crystals by the method of Hyper Raman spectroscopy. The 3L0 phonon line was detected in CdS at the near resonance conditions.

We report the observation of the size evolution of the laser light formed clusters. A cell containing sodium vapor and the buffer gas (He) under high pressure was used in the experiment. Changes of the radius and of the density of transient clusters were observed via the time evolution of the intensity of right-angle scattered light. The rate of the cluster radius growth was found to vary from 0.012 to 0.1 pm/s. PACS: 36.40.+d, 31.70.Hq, 64.70.-p.

The automatic measuring device for the control of technology and for polishing surface roughness measurements has been described in this work. This device has very high sensibility and allows to measure rms ( root mean squared ) roughness U equal some angstroms. There is noncontactive and nondestructive photometric measurement. It is based on the differential scattering measurement. We develop the theoretical framework for the device to definite absolute quantity rms roughness a and correlation length a. It has been demonstrated that this device together with method allows to measure surface roughness of samples from different materials including transparent ones for laser light. It was foreseen that the scattering from the untest surface of sample would be led out. It allowed to measure the transparent samples without sputtering reflective films. Sensibility of defination of rms roughness is about 1 A, with precision about 30%. The results of this measuring method were compared with ones obtained with other methods and it was received good agreement. The results of the investigation of the surface samples roughness with different technology has been described. This method of measurement has an industrial application for control different surfaces roughness.

We describe different atomic and molecular spectroscopy experiments we performed by means of smiconductor diode lasers. In particular, we discuss the questions of high spectral resolution, for accurate measurements of fine spectral structures, and high sensitivity, which is important for low absorptions detection. The results we obtained demonstrate that the specific characteristics of these laser sources make them ideal tools for spectroscopy.

Computer controlled apparatus for laser flash spectroscopy has been constructed. Nitrogen laser (energy 1 inJ, pulse width 1 ns) is used both for excitation of the sample and for pumping the tunable dye laser which serves as a source of monitoring light. Two different scans are possible: (i) a mode with a fixed wavelength of the inonitoring light - the temporal evolution of the transient absorption in the range from -2 ns up to 100 ns can be observed by changing the length of the variable self-compensating optical delay line, (ii) a mode with a fixed time delay - the corresponding transient absorption in the range 380 - 800 nm can be measured. For illustration, time evolution of transient absorption and time resolved spectra of benzanthracene in ethanol are reported.

Resonance ionization of atoms confined in a hot cylindrical cavity is a very efficient and selective technique for trace analysis. Several applications of this method have been tested or are presently under investigation. An efficiency of 14% was obtained for technetium. An efficient path for rnance ionization of tin was found, leading to an autoioniing state at 59375.9 cm1. The high efficiency makes the baer ion source suitable for trace analysis of actinides in the environment. In all cas surface-ionized background has to be suppresoed to avoid isobaric interferences. Therefore a new laser ion source has been developed with a cavity made ofextremely pure pyrolytically coated graphite.

The influence of amplitude and phase lattices on kinetics generated by dye lasers with distributed feedback radiation is delimited in the present paper. It is shown that generation regime of single impulses of 200 ps is realized when amplitude lattice plays the major role in the feedback and in the case of little above threshold of pumping. In the case of primary contribution to the feedback of thermal phase lattice the nonstructural impulse of nanosecond duration is generated.

Described are procedure and technique capable of analyzing cavity spectra,making coefficients of total and diffracted cavity loss measurements,reflectivity measurements of low-loss highly reflecting mirror coatings and gain measurements of active substance. Measurer also makes it possible to control a level of selection, a quality of mirrors alignment and an accuracy of cavity monoblock making. The apparatus analyzes transmission or reflectivity spectra of controled cavity, directly measure output pulse width proportional to cavity linewidth (FWHM intensity) and time proportional to frequency distances apart the transmission or reflectivity lines. We develope the theoretical framework for the device and discuss in what conditions and to what extent the output pulse width and the time proportional to frequency distances apart the lines measuremcits represents a true measure of cavity parameters. Current apparatus provides a cavity loss and gain resolution 0.0001 and spectral resolution 10 kHz.

Results of a self-injection locked, passively switched Ti:sapphire laser investigations are presented in this paper. Shortening and stabilization of pulse duration have been achieved using the SBS cell innside of the laser cavity. The main advantages of this laser and its features are shown.

We report on a new technique for measuring the cathode dark space width and the variation of ground state atomic density within it by measuring the ionization current generated by laser photoiomzation of neutral ground state metallic atoms. The technique is supported by a theoretical model of charge displacement in the dark space. Measurements of dark space width with respect to pressure, current and nature of the buffer gas are presented for an uranium hollow cathode discharge (HCD). Results of variation in density of ground state neutral uranium, in the dark space, versus current and pressure in Xe are also given. These results are of interest when using photoiomzation currents in the HCD dark space for laser spectroscopy, such as photoiomzation studies of refractory elements like uranium.

The wide bandwidth single color multiphoton ionization spectrum of uranium was measured in the spectral range of Rhodamine 6G dye, using the fast ( iO sec.) pulsed optogalvanic effect generated by photoionization in the dark space ofa hollowcathode discharge (HCD). Results indicate that for this spectral range (between 570and 610 nm) the optogalvanic multiphoton ionization spectrum is very rich. A list of the 74 most significant photoionic lines is presented. With the help of published levels and using three resonant or quasi-resonant photons ionization schemes, proposed assignments of these lines are also presented. The line at 591,54 nm is a special case which is discussed in more detail.

Progresses in remote sensing of the atmosphere using the Udar (Light detection and ranging) technique closely follows progresses in Laser technology. We developed a mobile DIAL (differential absorption Lidar) system, based on high repetition rate Excimerpumped dye lasers, for performing 2D and 3D-mappings of concentration of NO, N02, S02, and 03. The high sensitivity of the system has been used for numerous environmental studies and measurement campaigns, providing for the first time a direct correlation between emission and immission. Attractive results have been obtained under urban conditions, because of the presence of strong concentration gradients, and fast fluctuations due to traffic. A comparative study between Lyon, Stuttgart, Geneva and Berlin will be presented. In particular, the Berlin-campaign demonstrates the possibility of detecting unknown emitters and monitoring exportation-importation processes of atmospheric pollution. A new stationary DIAL system has been recently constructed and implemented on the top of a building in the center of the city Leipzig. It will routinely perform concentration mappings of nitrogen oxides, sulfur dioxide and ozone, giving access to long term evolution of pollution distributions.

By the use of commercial A1GaAs diode lasers and short radiation path-length, frequency modulation (FM) absorption spectroscopy has been performed in the near infrared to study the overtone absorption bands of molecules interesting as environmental sensing tracers. Our measurements concern water vapor resonances around 820 nm, methane around 780 nm and 860 nm, and ammonia around 790 nm. Pressure broadening coefficients have been extracted by using different buffer gases like air, N2 , He, and by varying their pressure between 10 and 760 Torr. A x2 fitting of the absorption line shapes has been used for this purpose by the aid of a simple fitting function. Finally an estimation of the sensitivity of the technique is made.

The design of a newly constructed high performance portable Vis-NIR multiple wavelength sunphotometer is presented. The device measures the incoming flux of direct solar radiation within narrow spectral intervals set by bandpass interference filters. These intervals correspond to the main windows of the visible and near-infrared attenuation spectrum of the atmosphere and to the selected water vapor absorption bands. The instrument's optical features and performance are described. It is explained why the most important parts of the device should be carefully stabilized thermally (detector and amplifier within filters and signal processing unit within to avoid biasing of the solar signal. The overall accuracy of the photometer's output is derived to be better than 0.1% to match requirements in the NIR.

The molecular absorption spectra of pH dyes, employed for ammonia sensing are investigated. Differences of absorption spectra of Bromothymol Blue and Bromocresol Purple dyes, dissolved in water and entrapped in Polymethylphenylsiloxane film are discussed. Correspondence of dye-films absorption bands shape to the Gauss distribution shape in the spectral region of light source emission band was determined.

Incorporation of naphthalene and indole into polyethylene makes it possible to observe phosphorescence of both molecules in the temperature range up to 213 K. Considerable difference between low-temperature fluorescence spectra of indole in polyethylene vs. 3-methylpentane suggests the formation of aggregates in the latter.

ABSTRACT We found that any uniform stressed area in loaded birefringent material observed in a polarized, dispersed light shows an extinction effect (black fringes) for different light wavelength A. The shape, speotral position of the fringes and their number depends on value of the stress. The analysis and explanation of the effect were done. The laboratory, computer aided spectrometer was build for making precise measurements for different loading conditions; the results of the measurements are described. The application of the effect as an uniaxial force sensor is proposed.

The spectrophotometric technique used in pulse oximetry makes it possible to determine noninvasively and continuously the oxygen saturation of arterial blood. This technique utilizes a set of the living blood-supplied tissues as an object to be measured. From the metrological point of view, the sensing efficiency, spectrophotometric processing quality, and object modelling are of great importance in reliable solution of the specific interdisciplinary problems. In this paper the main results of the authors studies concerning the optical part of measuring system have been described against a background of the reviewed generally valid principles.

In optical planar and/or channel waveuides, determination of two parameters such as: the depth and the waveguide index with the use of the rn-line spectroscopy (prism coupling method) involves measuring of at least two coupling angles of the guiding modes. Most of integrated optical devices operate in sigle-mode regime but such devices developed for 2-nd and 3-rd transmission windows are multimodal within the VIS range thus the conventional rn-line study with the use of the He-Ne laser yields in evaluation of the waveguide parameters under examination. However, the conventional m-line procedure of the determination of the waveuide parameters fails for single-mode structures developed for the application within the VIS-range. A method presented in the paper involves an additional two-beam interferometric examination of the slab with a waveguiding structure. The interference of the beams reflected from the upper and lower surfaces of the slab results in a fringe pattern. Within the region of the waveguide boundary one observes the fringe shift related to the difference of optical paths of the beams in- and outside of the waveguide. The microscopic study of that fringe pattern results in an additional relation of the waveguide depth and its index. A substitution of the waveguide depth by the last relation results in a modified modal eqaution for the waveguide index that can be solved by conventional numerical methods.

We consider total internal reflection of a monochromatic plane wave from an isotropic nonlinear medium with cubic nonlinearity. Hodograph of the electric field is found from the expression for energy density of the field. Possible values of angle of incidence are found. Essential differences between waves in focusing and defocusing media are pointed out and discussed. It is shown that the phase of the refraction coefficient is a multi-valued function of the angle of incidence and power of the incident wave.

Based on the angular backbone taken from the triangular Sierpinski gasket, several seLf-similar structures are disigned, corresponding diffraction screens are made, and the Fraunhofer patterns as power spectra of them are given. Based upon a viewpoint of generative production and by means of the ui-branched displacement operation, we have found the recurrence formulae of spectral structure factor for these angular fractals. As a example, the recurrence formulae of power spectra for a coherent point group is given, corresponding a series of curves as well as an isogram are plotted. The analysis of result shows that the power spectra of this fractal point group has a rotation symmetry and a mirror symmetry, and appears a period doubling phenomenon which follows the process of generative production.

Four styles of fractal informations are constructed on the Cantor sets as time axis. Based upon a view point of generative production, we have found the recurrence formulae of spectral structure factor and of spectral shape factors of them, plotted a series of curves of the structure factor and four series of curves of the spectral functions. From the comparison and progression of these curves, it can be seen that the structure factor plays a ground role, and the shape factor plays a modulatory role, there are a competitive phenomena between generations in frequency domain. This investigation provides a basis for further understanding of the features of fractal informations by a new representation such as frequency domain.

Using infrared double-resonance spectroscopy on the time-scale of picosecon$Is the ultrafast dynamics of hydrogen bonds In condensed matter is directly investigated for the first time. We have developed a two-colour pump-probe technique with independently tunable Intense pump ( iO W/cm2) and weak probing pulses /1/. Within the tuning range of 1.4 - 4 jim novel spectroscopic information Is obtained by the help of temporal (' 3 ps), spectral ( 5 cm1 ) and polarization resolution. New spectral features not accessible for conventional IR spectroscopy are observed, e.g. excited state absorption, induced hot bands and, most important, spectral holes. In this way photophysical (vibrational energy transfer) and IR-photochemical processes are Investigated. Structural information is derived from the separation of inhomogeneous and homogeneous broadening effects of the Infrared bands.

During the past few years the remote sensing techniques have become an important tool in atmospheric monitoring. Depending on the materials to be detected and the requirements of measurement e.a. distance, environmental circumstances, velocity, etc., there are several methods capable for this purpose.

A review of theoretical and experimental works on the polarization photon-echo spectroscopy (PPE spectroscopy) is carded out. The main attention is payed to the following advantages of the PPE spectroscopy. First, the PPE spectroscopy, free of the influence of the inhomogeneous spectral line broadening, allows to make the high precision measurements within the envelope of a inhomogeneously broadened spectral line. Second, the high resolution ability of the PPE spectroscopy, directly in the temporal field, unables to accomplish the investigations of the fast relaxation processes, when ultrashort nano- and picosecond exciting pulse are used. Third, in the PPE spectroscopy the investigated relaxation processes are not subjected to the perturbing action of the intensive laser radiation. Farther, it is necessary to note the flexibility of the PPE spectroscopy consisting in the existence of a great number of various methods used for receiving different spectroscopic information. Finally, as far as the signal intensifies of the photon echo and of its variants are proportional to the squared number of the resonant atoms (molecules), it secures the definite advantages for the PPE spectroscopy as compared to the spectroscopk methods based on the non-coherent phenomena (especially for low pressure a gas considered). The possibilities of new experiments on photon echo and its variants aimed for obtaining a detailed new spectroscopic information are discussed.

Crystals with colour certres (CC) are well known in the field of solid state tunable lasers. Colouration of the bulk crystals was obtained using Roentgen, gamma or neutron irradiation. Also the electron lithography that includes electron beam action on polymeric materials has made a great progress. The high resolution achieved for resulting microelectronic structures was provided by the resolution of electron beam focusing but was partially failed in polymeric matrices due to their chemical properties during consecutive processes of stabilization of the exposed areas.

A double-refractig interference system with variable wavefront shear has been adapted to wave- lengthmetry ot nochromatic light. The interfrixige spacing is directly measured while the wavelength is read out frog a calibration plot or a data table stored in the computer mery. The proposed technique is especially suitable or aauring the peak wavelength o nocbroatic intererence filters. The measuring accuracy as good as Al = m is easily achievable.