FTIR spectrum of the nu(4) band of DCOOD

The FTIR spectrum of the nu(4) band of deuterated formic acid (DCOOD) has b een measured with a resolution of 0.004 cm(-1) in the frequency range of 11 20 to 1220 cm(-1). A total of 1866 assigned transitions have been analyzed and fitted using a Watson's A-reduced Hamiltonian in the I-r representation to derive rovibrational constants for the upper state (nu(4) = 1) with a s tandard deviation of 0.00036 cm(-1). In the course of the analysis, the con stants for the ground state were improved by a simultaneous fit of microwav e frequencies and combination differences from the infrared measurements. D ue to the relatively unperturbed nature of the band, the constants can be u sed 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 s trong enough to be observed. The band center is at 1170.79980 +/- 0.00002 c m(-1). (C) 1999 Academic Press.