Ã 2Π←X̃ 2Σ+ infrared electronic transition of C2H

Abstract

High resolution laser spectroscopy of the C2Δ-X2Σ+ transition of CaOH and CaOD: Vibronic coupling and the Renner-Teller effect

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

“…Assuming that their calculated bond lengths were accurate within a few thousandths of an ~ngstr6m and that the predicted stretching frequencies were true within 3% (and the bending frequency within I0 percent), the authors questioned the interpretations of the experiments leading to the values of these structural parameters being outside of these error limits. This concerned foremost the ground state vibrational frequency vl =3612 cm -1 determined by Jacox [16] from the observed infrared argon matrix spectra and v2=375 cm -~ obtained by an analysis of the laser infrared spectrum of CzH [22]. A completely new assignment of the observed bands was proposed.…”

“…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.…”

“…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.…”

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

“…The first spectroscopic gas-phase detecti, on of C2H in the laboratory was carried out in the microwave [18] and in the far-infrared [t9] region. Vibrational and electronic spectra of the ethynyl radical in the gas phase were identified by color laser spectroscopy by Curl and coworkers [20][21][22][23][24][25] and have recently been extensively studied in several laboratories [26][27][28][29][30][31]. Results of experimental investigations of the hyperfine structure in the ethynil spectra have been published in [32][33][34][35][36][37][38][39].…”

How Complex can be the Unimolecular Decomposition of a Simple Molecule? The Case of Acetylene. An Electron Impact and PIPECO Investigation

“…Several quantum mechanical [21][22][23] and spectroscopic [24][25][26] investigations of this radical have been reported. The lowest excited state should level at about 0.5 eV above the ground state and should have the 2 ∑ multiplicity and symmetry.…”