In the past europium doped materials have been tailored in our group, which could exhibit the highest spectral
storage densities known to date. In these materials, europium exists in both doubly and triply ionized states. Therefore, it
is necessary to control the relative concentration of Eu2+ and Eu3+. Due to accidental overlap of Eu2+ and Eu3+ optical
transitions in this medium optical spectroscopy cannot be used to determine their relative concentration. For highly
enriched europium samples, such a ratio can be determined by Mössbauer spectroscopy. However, at very low
concentrations of the order of 0.01% of Eu in MgS that are necessary for these materials, conventional Mössbauer
spectroscopy requires prohibitively long data acquisition times. In this article, we present and compare the ways of
solving this problem with conventional and the time domain Mössbauer spectroscopy using Nuclear Forward Scattering.
The synchrotron of the Advanced Photon Source at Argonne National Laboratory has been used as the source of high
intensity, coherent and monochromatic gamma rays in NFS experiments. It is shown that in time domain Mössbauer
spectroscopy the data acquisition times can be reduced by two orders of magnitude or more. This is of paramount
importance for Mössbauer spectroscopy of very small samples or the samples with very low concentrations of the active
Pulsed Laser Chemical Vapor Deposition (PLCVD) has been used to fabricate single atoms doped nanoparticles of magnesium sulfide. These particles were dispersed in optically transparent Poly-methyl-methacrylate (PMMA) films for near field nano-microscopy such that each nanoparticle doped with a single europium atom falls in the focusing range of the near field microscope. By atomic tailoring, the concentration of the doubly ionized europium, Eu2+, has been maximized in these nanoparticles. The energy and the oscillator strength of the 4f7-4f65d1 electronic transition has been tailored to maximize its addressing by photons in single atom spectroscopy experiments. Results have been presented on the fabrication of these single atom doped nanoparticles and their spectroscopy by laser excited fluorescence technique. Studies of a single Eu2+ ion by confocal micro-spectroscopy are in progress.
Results have been presented on isolating rare earth atoms in small numbers in semiconductor
nanoparticles so as to use their organized arrays as hardware for quantum computing. We have
tailored atomic states of rare earths, fabricated nanoparticles where these atomic systems are
incorporated in small numbers and have patterned arrays of nano-holes on semi-conducting and
polymer surfaces to encapsulate these rare earth doped nanoparticles. Results are presented on
fabrication, microscopy and spectroscopy of these structures.