Investigations of several infrared bands of 12C2H2 and studies of the effects of vibrational rotational interactions

Infrared Spectra of 14C2H2 and 12C14CH2 : The ν1 5 Band

“…The calculated band origin frequencies, band cen ters and molecular constants are summarized in Table 4, together with the respective data for 12C2H2, 13C2H2 and 12C 13CH2. It can be seen that the errors of our data are at the level of those for 12C2H2, re ported by Palmer et al [5], in accordance with an identical resolution of 0.04 cm 1 for both measure ments.…”

Full dimensional Franck-Condon factors for the acetylene $\tilde{\mathbf {A}}$Ã 1 A u—$\mathbf {\tilde{X}}$X̃ $\mathbf {^1\Sigma _g^+}$Σg+1 transition. I. Method for calculating polyatomic linear—bent vibrational intensity factors and evaluation of calculated intensities for the gerade vibrational modes in acetylene

“…The vibrational q 4 term that mediates the vibronic transition is treated in the vibrational integral and we obtain the same result as in Eq. (6). When viewed in the diabatic picture, it becomes clear that the vibronic mechanism by which theÃ-X becomes electronically allowed is the same mechanism that causes the vibronic distortion of theÃ-state equilibrium along the π g trans-bend coordinate.…”

“…65 In order to reproduce the results of Watson, we first used theÃ-state geometry and harmonic force field from Tobiason et al 66 Using these force fields, we obtained elements for the gerade block of D (a-s) and δ (a-s) that agree with those obtained by Watson to within a phase factor of ±1. 46 The phase factor Antisymmetric stretch b u 3032.4 ν 6 Cis bend b u 801. 6 FIG.…”

Full dimensional Franck-Condon factors for the acetylene $\tilde{\mathbf {A}}$Ã 1 A u—$\mathbf {\tilde{X}}$X̃ $\mathbf {^1\Sigma _g^+}$Σg+1 transition. II. Vibrational overlap factors for levels involving excitation in ungerade modes

“…As the number of quanta in ν 4 increases, access to the extreme counter rotator shifts to higher-lying polyads of theX state, and the maximum counter rotational character is found in the polyad with approximately N B = 2v 4 . On the other hand, the fraction of the bright state that corresponds to the extreme local bender (shown in the first column of Figure 4) depends very sensitively on the number of quanta in ν 6 , and the maximum local bender character is found in the polyad with approximately N B = 2v 6 .…”

“…The trans-bend is higher in frequency than ν 4 and ν 6 and does not interact strongly with the B n polyads at low vibrational quanta. However, the cis-trans isomerization gives rise to very strong negative anharmonicity between modes ν 3 and ν 6 In Figure 1, calculated emission intensities to the dominant progressions observed from 2ν 3 + ν 6 and 3ν 3 …”