Erratum: Rotational analysis of the A ̃ ← X ̃ system of C2H [J. Chem. Phys. 8 2 , 3479 (1985)]

Z Phys D - Atoms, Molecules and Clusters

Peyerimhoff

Buenker

1992

Abstract.A purely ab initio study of the vibronic structure of the C2 H spectrum in the region up to 7000 cm -~, which is complicated by the coupling of the X 2 Z + and A 2H systems, is presented. The potential surfaces for the three lowest-lying electronic states 12A', 22A ' and 12A" correlating with X 2L" + and A 2H at the linear molecular geometry are calculated for the various geometrical distortions by means of the multireference configuration interaction (MRD-CI) method. These adiabatic surfaces are transformed into suitable diabatic counterparts. An approach is developed for a simultaneous treatment of three electronic states coupled via the bending and C-C stretching vibrations. Spin-orbit splitting of the vibronic levels and the vibronically averaged values for the hyperfine coupling constants are computed. The results obtained in this study enable a reliable explanation of the available experimental findings of the C2 H spectrum and predict a number of features to be verified by future experiments.

Section: C~'~'~" =0mentioning

confidence: 99%

Analysis and predictions of the vibronic spectrum of the ethynyl radical C2H by ab initio methods

Z Phys D - Atoms, Molecules and Clusters

Peyerimhoff

Buenker

1992

“…Vibrational and electronic spectra of the ethynyl radical in the gas phase were identified by Carrick et al [21,22] and Curl et al [23]. Employing colour center laser spectroscopy, the authors observed in an argon discharge over polyacetylene five bands in the region between 36004200cm-a (3692, 3773, 3785, 4011 and 4106 cm -~) and assigned them to the A 2 H~X 2 2 2 + electronic transition.…”

Section: Introductionmentioning

confidence: 97%

“…The bending frequency of the ground electronic state was estimated from the /-type doubling constant (where vl=3612cm-1 and v3 = 1848 cm -1 have been assumed) and a value of 375 cm-1 [22], or 389 cm-1 [23] (interpreted as the lower limit) was obtained. It is interesting to note that no band was observed in the region near 3612 cm-1 in which Jacox [16] found the absorption assigned to the C--H mode.…”

Section: Introductionmentioning

confidence: 99%

Ab initio calculation of the potential surfaces for low-lying valence electronic states of the C2H radical

Thümmel

Z Phys D - Atoms, Molecules and Clusters

Peyerimhoff

et al. 1989

The results of an extensive CI treatment for the three lowest-tying electronic states I ZA', 2 2A' and 12A" of C2 H are reported. Two-dimensional C -C stretching/bending potential surfaces for these species are calculated. Electronic dipole and transition moments are computed as a function of the bond angle and the C -C bond length. The results serve as a starting point in a theoretical analysis of the rovibronic structure of the longwavelength spectra of CzH.

“…In the experimental arrangement it is possible to shift the laser upper states the value of the spin-orbit coupling constant frequency down by 90 MHz, using an acousto-optical modu-is 5.4 cm 01 in the 2 P (3693 cm 01 ) level and 7.2 cm 01 in the lator for sideband generation. These sidebands enabled us 2 P (3600 cm 01 ) level (13,14). The lower rotational levels to determine the tuning rates and the tuning directions of can be described in a Hund's case (a) coupling scheme, but the observed transitions, which was very helpful in guiding for higher J values Hund's case (b) is more suitable.…”

Section: Discussionmentioning

confidence: 97%

Faraday Laser Magnetic Resonance Spectroscopy of Vibrationally Excited C2H

Pfelzer

Havenith

Journal of Molecular Spectroscopy

et al. 1996

The gas phase spectrum of the C 2 H radical in the region between 3191 and 3342 cm 01 has been studied using a Faraday LMR spectrometer with a CO overtone laser. The C 2 H molecules were produced in an electric dc glow discharge of normal type containing a mixture of helium, acetylene, and hydrogen. We observed two bands of the X 2 S / r A 2 P electronic transition with origins at 3321 and 3229 cm 01 . The lower level of both bands was the first excited bending level of the electronic ground state X. The upper levels were assigned to two 2 P vibronic levels with term values of 3693 and 3600 cm 01 , respectively. They correspond to mixtures of vibrationally excited levels of the X electronic state with the lowest vibronic level of the first excited electronic state A. From the analysis of the spectra we could determine the orbital g factors of the upper levels. These parameters are a very sensitive measure for the mixing between the X and A electronic states. The experimentally derived values were compared with theoretical values, obtained by ab initio calculations, and could be explained by the theoretical model using an improved energy distance between the X and A states. ᭧