Spectroscopic Studies of Neutral and Ionized Solid Hydrogen and Gasesous Hydrogen Plasmas

This is the final report and the total summary of my research effort with graduate students on my Air Force grant F49620-94-1-0145 from February 1, 1994 to July 31, 1997. According to my proposal submitted on March 31, 1993, this three year project was to study pure vibrational Qv(0), J=0 -0 in para-hydrogen (p-H2) crystals. Such transitions are clearly highly forbidden in the ordinary electric dipole selection rules and the transitions have to be of the second-order Raman type in which the transition moment M is given by the Kramers-Heisenberg formula. In order to observe such transitions, we need an extra electric field E' in addition to the laser radiation field E. We used a variety of extra electric fields such as laser radiation field (stimulated Raman effect), external D.C. electric field (Condon effect), the quadrupolar field of ortho-hydrogen (o-H2) impurity, and the Coulomb field of electric charges deposited in the crystals by gamma ray radiolysis. Because of the nature of p-H2 as quantum crystals the field-induced spectra can be observed with extremely high resolution, and the observed intricate structure provides information on vibron dynamics, intermolecular interactions, crystal field interactions and crystal distortions with unprecedented clarity and accuracy. Most of these objects have been experimentally achieved and provided enormous amount of observed results to be analyzed and understood. Our work has also led to application of the high resolution solid hydrogen spectroscopy to matrix spectroscopy and to nonlinear optics.