Temperature and time effects on the rovibrational structure of fundamentals of H 2O trapped in solid argon: hindered rotation and RTC satellite

Abstract

The ν 1, ν 2 and ν 3 modes of H 2O trapped in solid argon are re-examined in the temperature range 6–30 K. We confirm that the broad structure with two maxima around 1657.4 and 1661.3 cm −1, which undergoes nuclear spin conversion of the high frequency components to the low frequency ones at 6 K, can be assigned to a rotation–translation coupling (RTC) structure. The doublet splitting and the frequencies exhibit a strong matrix dependence, and we observed new lines arising from the J=2 levels. Nuclear spin conversion has been successfully used to determine the energy difference between the lowest rotational levels in the vibrational ground state. The hindered rotation was modelled to obtain effective rotational constants. However, this model is not detailed enough to reproduce frequencies of transitions involving J=2 states.