The Spectrum of Hot Water: Rotational Transitions and Difference Bands in the (020), (100), and (001) Vibrational States

Abstract

Analysis of the hot H216O spectrum, presented by Polyanskyet al.(1996,J. Mol. Spectrosc.176,305–315), is extended to higher vibrational states. Three hundred thirty mainly strong lines are assigned to pure rotational transitions in the (100), (001), and (020) vibrational states. These lines, which involve significantly higher rotational energy levels than were known previously, are assigned using high-accuracy variational calculations. Transitions in (020) are assigned up toKa= 18, compared with the maximumKaof 10 known previously. Crossings of vibration–rotation energy levels result in the observation of extra intensity-stealing transitions. In particular, this leads to the assignment of (020)–(100) and (100)–(020) rotational difference band transitions in addition to the conventional pure rotational lines in (020) and (100) states. These extra lines increase the number of transitions and they are likely to complicate the pure rotational water spectrum in higher excited vibrational states to an even greater extent. A few lines from our previous work on the pure rotational spectrum of hot water in the (000) and (010) vibrational states are also reassigned and some further assignments are made.