Handheld Raman spectroscopy’s value for rapid field screening by safety and security personnel is well understood as evidenced by its implementation across the globe. Though Raman spectroscopy has the ability to nondestructively identify samples through transparent packaging, in real world scenarios challenging samples are frequently encountered. Raman screening must be effective for samples in a variety of packaging and for samples with coloration or impurities that give a high fluoresce that can overwhelm the Raman signal depending on the excitation laser wavelength. See through Raman technology has been developed to enable measurement through opaque packaging, sampling a larger area and with a deeper penetration depth of the Raman signal. Using a design of collinear sample illumination and Raman scattering collection at a higher efficiency, and spread over a larger sampling area, there is a lower power density of illumination on the sample, reducing issues of sample heating that can be problematic for dark samples. The measurement of a larger sample area provides more reliable identification of solids that are often inhomogeneous. This see through Raman technology and the use of a longer laser wavelength excitation overcomes many of the difficulties encountered in use of Raman spectroscopy for field testing.
We present a new type of handheld laser-induced breakdown spectroscopy (LIBS) spectrometer for developing mobile atomic spectroscopy solutions for real world applications. A micro diode-pumped passive Q-switched solid-state laser with high repetition rate of well above 1 kHz in comparison to 1-10 Hz as used in a traditional LIBS instrument is employed to produce a train of laser pulses. The laser beam is further fast scanned over a pre-defined area, hence generating several hundreds of micro-plasmas per second at different locations. Synchronized miniature CCD array spectrometer modules collect the LIBS signal and generate LIBS spectra. By adjusting the integration time of the spectrometer to cover a plurality of periods of the laser pulse train, the spectrometer integrates the LIBS signal produced by this plurality of laser pulses. Hence the intensity of the obtained LIBS spectrum can be greatly improved to increase the signal-to-noise ratio (SNR). This unique feature of the high repetition rate laser based LIBS system allows it to measure elements at trace levels, hence reducing the limit of detection (LOD). The increased signal intensity also lessens the sensitivity requirement for the optical spectrometer. In addition, the energy of the individual laser pulse can be reduced in comparison to traditional LIBS system to obtain the same signal level, making the laser pulse less invasive to the sample. The typical measurement time is within 1 second. Several examples of real world applications will be presented.
Spectroscopic studies have been done on crystallization and other reactions that undergo multiple phase changes. As the reaction opacity changes the spectral information is processed to determine which mode of measurement is optimal: reflectance or interactance immersion. A near IR spectrophotometer equipped with a unique probe is used which allows for optimal process monitoring with a single probe, rather than using multiple process interfaces to accommodate the change in the reaction medium. A with any near-IR method, models are created to allow for reproducible predictions of the phase changes that occur, and can also be used to quantitate the extent of reaction, the system composition, and other parameters.