High-resolution Fourier-transform spectroscopy of solid parahydrogen in the first overtone region

The first vibrational overtone spectrum of solid parahydrogen with various low orthohydrogen impurity levels has been studied in the range 7900 endash 10000 cm-1 using a White-type external multireflection system with a 34.8-cm sample path length. We were able to detect extremely weak features, namely, the Y1(0) at 7991.85 (1) cm-1, and the double transitions U1(0) + Q1(1), U1(0) + S1(0), U1(1) + Q1(0), and Q1(0) + Q1(0). The Q1(0) + Q1(1) and Q1(1) + Q1(1) double transitions were resolved. We obtained a rich orthohydrogen satellite spectrum associated with the transitions Q2(0) and Q2(1) near 8060 cm-1. An analysis and assignment of these satellite transitions are presented. The double transitions of the type Q1(J) + Q1(J') (J,J' = 0,1) are located in the spectral region around 8300 cm-1. The most remarkable features here are the Q1(1) + Q1(1) transition, which consists entirely of fine structure, and the Q1(0) + Q1(0) transition, which, to our knowledge, has an intensity that cannot be accounted for by previously proposed mechanisms. Finally the thermal shift of all of the above-mentioned transitions was investigated by lowering the sample temperature from 12.5 K down to 6.5 K while taking spectra. The influence of the change of temperature on the line positions, linewidths, and interaction parameters of solid hydrogen is discussed. copyright 1997 The American Physical Society