With the high resolution Fourier transform spectrometer now available the vibration-rotation spectra of many of the heavier molecules can now be resolved. In previous mid-infrared rotation analysis of the fundamentals of nitrogen trifluoride (NF3) resolutions ranging from 0.05 to 0.2 cm-1 were used (1,2). The high resolution Fourier transform spectra of v1 and v3 have been recorded with a Bomem interferometer with an apodized resolution of about 0.004 cm-1. The v1 parallel band is centered at 1032 cm-1 and has the classic appear-ance of a parallel band with small changes in the rotational constants. The higher resolution spectra reveals the K structure in the different branches. From the intensity alternation, definitive numbering of the K branches could be obtained and more accurate rotational and distortion constants obtained from the rotational analysis. The v3 perpendicular band is centered at 909 cm-1 . With the higher resolution spectra the rotational structure that is observed under lower resolution is shown to be due to the PQ branches. The RQ branches are not apparent. The large intensity variation in the Q branches is due to ℓ-type resonances. The intense PQ branches versus weak RQ branches indicate that the Q,-type doubling constant q3 is negative, as calculated earlier (3,4). The ς3 constant (.81) determined from the sum rule is too large to explain the smaller separation observed (6.4 cm-1 versus 4.7 cm-1). A strong Coriolis perturbation is indicated, probably with the 2v4 (A1) vibration at 984 cm-1. The analysis of this vibrational band is in progress and will be reported.

Date Published: 1 December 1989
PDF: 1 pages
Proc. SPIE 1145, 7th Intl Conf on Fourier Transform Spectroscopy, (1 December 1989); doi: 10.1117/12.969612

Published in SPIE Proceedings Vol. 1145:
7th Intl Conf on Fourier Transform Spectroscopy
David G. Cameron, Editor(s)