Journal of Molecular Spectroscopy 
         -- Oct. 1997 -- vol.185, no.2, pp. 356-69

Intensity measurements of Delta l>1 transitions 
of several isotopomers of HCN

Maki, A.; Quapp, W.; Klee, S.; Mellau, G.C.; Albert, S.

The intensities of the forbidden Q-branch transitions 02^2f/0-00^0/0, 
12^2f/0-00^0/0, and 02^2f/1-00^0/0 for HCN have been
measured. The intensities of the 02^2f/0-00^0/0 transitions of DCN,
D^13/C^15/N, and H^12/C^15/N were also measured, as well as
the 02^2f/1-00^0/0 transitions of H^12/C^15/N and H/sup
13/C^15/N. These Q-branch transitions are forbidden even when the
effects of l-type resonance are considered so they must get their intensity
from some other Coriolis interactions. The much stronger P- and R-branch
lines for the e levels of these same vibrational transitions were also
measured and they are shown to get most of their intensity from l-type
resonance. However, the same Coriolis resonance that gives intensity to the
Q-branch transitions seems to affect the Delta J=+or-1 transitions as shown
by the difference in the intensities of the Delta J=+1 and Delta J=-1
transitions. Measurements of the intensity of the 03^3e/0-00^0/0 and
03^3f/0-00^0/0 transitions shows that they derive most, but perhaps
not all, of their intensity from l-type resonance. An unsuccessful search
for forbidden Delta J=0, e-e transitions for the strong 10^0/0-00/sup
0/0 band shows that there is no detectable mixing of the e and f levels

Doc. Type Journal Paper ; Experimental
Publisher Academic Press  Coden JMOSA3  ISSN 0022-2852

Classification codes A3370F; A3520B; A3520P

Indexing 
hydrogen compounds; isomerism; isotope effects; spectral line intensity; 
vibrational states;
intensity measurements;  Delta l>1 transitions; isotopomers; HCN; 
forbidden Q-branch transitions; l-type resonance; Coriolis interactions; 
P-branch lines; R-branch lines; vibrational transitions; e-e transitions