CONDON MODULATION SPECTROSCOPY OF SOLID HYDROGEN AND MEASUREMENT OF THE TEMPERATURE-DEPENDENCE OF THE Q1(0) TRANSITION

The Condon effect, in which an electric field induces otherwise forbid den transitions, has been used for inducing and modulating the Q1(0) v ibrational infrared spectrum in para-H-2 crystals. The field induced s pectrum obeys the exciton momentum rule, DELTAk = 0, and is very sharp . The modulation method has greatly improved the sensitivity and simpl ified the experiment. The method has been applied to study the tempera ture dependent frequency shift and broadening of the spectral line. Th e observed frequency shift has been explained as due to variations of matrix shift and vibron hopping frequency.