FTIR Spectrum of the nu4 Band of DCOOD.

The FTIR spectrum of the nu4 band of deuterated formic acid (DCOOD) has been measured with a resolution of 0.004 cm-1 in the frequency range of 1120 to 1220 cm-1. A total of 1866 assigned transitions have been analyzed and fitted using a Watson's A-reduced Hamiltonian in the Ir representation to derive rovibrational constants for the upper state (v4 = 1) with a standard deviation of 0.00036 cm-1. In the course of the analysis, the constants for the ground state were improved by a simultaneous fit of microwave frequencies and combination differences from the infrared measurements. Due to the relatively unperturbed nature of the band, the constants can be used to accurately calculate the infrared line positions for the whole band. Although the band is a hybrid type A and B, only a-type transitions were strong enough to be observed. The band center is at 1170.79980 +/- 0.00002 cm-1. Copyright 1999 Academic Press.