H. Hubner et al., MICROWAVE-SPECTRA, DIPOLE-MOMENTS, AND TORSIONAL POTENTIAL FUNCTION OF CIS-GLYOXAL AND CIS-GLYOXAL-D(1), Journal of molecular spectroscopy, 184(2), 1997, pp. 221-236
Citations number
34
Categorie Soggetti
Spectroscopy,"Physics, Atomic, Molecular & Chemical
Rotational transitions of cis-glyoxal, C2H2O2, and its monodeuterated
isotopomer have been detected by microwave spectroscopy, both in their
vibrational ground states and in their first and second excited torsi
onal v(7), as well as in their first excited v(5) bending states. Assi
gnments have been extended to high J and K-a quantum numbers which lea
ds to higher accuracy of the spectroscopic parameters than hitherto kn
own in the literature. Tunneling splittings of the torsion-vibrational
levels of 335 kHz for v(7) = 1 and of 42.6 MHz for v(7) = 2 have been
observed in the glyoxal spectra. These splittings are absent in glyox
al-d(1) as is expected for symmetry reasons, while local perturbations
are occasionally seen in all spectra. The electric dipole moment comp
onents have been determined for both molecules in several vibrational
states where a value of mu(b) close to 3.40 D was found in all cases.
The cis-trans enthalpy difference, Delta H = (18.60 +/- 0.57) kJ mol(-
1) ((1555 +/- 48) cm(-1)), was determined from absorption intensities
of glyoxal and glyoxal-di relative to those of the OCS molecule. A tor
sional potential function is given using Delta H, the cis tunneling sp
littings, and literature values for the frequencies of the trans and c
is torsional levels as input data. (C) 1997 Academic Press.