15min:

ADYA P. MISHRA AND ROBERT W. FIELD, Department of Chemistry and G. R. Harrison Spectroscopy Laboratory, Massachusetts Institute of Technology, Cambridge, MA02139, USA; S. V. N. BHASKARA RAO, R D'SOUZA AND T. K. BALASUBRAMANIAN, Spectroscopy Division, Bhabha Atomic Research Centre, Trombay, Mumbai, India-400 085.

Solid hydrogen as the archetypical molecular quantum crystal, seems to provide endless opportunities and challenges to experimentalists and theorists alike. The absorption process in solid hydrogens (H₂, D₂, HD, etc.) results primarily from induced dipole moments, although the small non-adiabatic allowed dipole contributes to the R-branch transitions for heteronuclear isotopomers. General and special expressions for the integrated absorption coefficients of all types of zero-phonon single and double transitions in solid H₂ have been derived earlier by different groups. These expressions would also be valid for D₂ and T₂ but the definition of ortho- and para- modifications with respect to J (rotational quantum number) will be different. For heteronuclear molecules, the ortho-para distinction does not exist and all the molecules in solid HD, HT and DT are normally in the J=0 state, thus simplifying the infrared spectra and theoretical analysis. However, extra complications arise due to the non-coincidence of the geometric charge center with the center of mass of the molecule. Further, since these molecules are not perfectly centrosymmetric, odd J transitions are also allowed in addition to even J transitions, which alone are possible in homonuclear counterparts like H₂. Although theoretical expressions for the intensities of certain transitions in HD have been derived by Poll and co-workers, so far no attempt is made to give general expressions valid for all transitions of similar types. Currently, we are attempting to derive closed-form expressions for the absorption intensities of single and double transitions in solid HD, HT and DT. The details will be discussed in the present paper.