Abinitio calculation of the vibrational structure in the electronic spectra of HCN and DCN between 1700 and 2000 Å

Abstract

. Can. J. Chem. 55, 3664 (1977).Ab initio SCF and CI calculations for the potential surfaces of HCN in ground and various l(n,n*) excited states are carried out using an A 0 basis of double-zeta quality augmented with various polarization functions. These results are then combined with transition moment data to allow for a Franck-Condon analysis of the vibrational structure of the lowest three electronic transitions in both HCN and DCN. The resulting intensity distribution is then compared with the corresponding experimental data reported by Herzberg and Innes. This work confirms the earlier conclusion of Schwenzer et al. that the upper state in the a + 3 band system is the lZ--'A" species, and not the ' A as originally believed. In addition a detailed mechanism for the observed predissociation of the a state is outlined, in which the gradual conversion of the n* MO of bent HCN into a pure hydrogenic 1s A 0 plays a key role. Arguments are also presented in favor of assigning the P e 8transition seen in DCN to a 'A-2'A' upper state with the same D + CN dissociation limit as for the 'Z--'A" species.

Theoretical calculation about the valence and rydberg excited states of hydrogen cyanide

“…The lowest excited state has à 1 A 00 symmetry at 6.44 eV and the configuration of (core)(3a 0 ) 2 (4a 0 ) 2 (5a 0 ) 2 (6a 0 ) 2 (1a 00 ) 1 (7a 0 ) 1 and the second and third ones also have 1 A 00 symmetry, while the B 1 A 00 X 1 R þ transition was reassigned later to the extension of the à 1 A 00 X 1 R þ transition on the basis of theoretical calculations. [10][11][12][13][14] Structural discrepancies between theory and experiment were found for the B 1 A 00 and C 1A 0 states. According to Herzberg, the bond angles of the B 1 A 00 and C 1A 0 states should be 114.5 and 141 , respectively, while Walshs calculations found two (nearly) linear excited 1A 0 states and one bent 1A 0 state, and none has the bond angle close to 141 .…”

Franck-Condon matrix elements for bound-continuum vibrational transitions calculated by numerical integration and basis set expansion techniques

“…The overall structure of the Franck-Condon factor distribution is very similar with respect to the location of the maxima and minima (Table 1). Further it is easy to include the electronic transition moment, which might exhibit a strong variation with internuclear distance, as it has already been done for transitions between bound states [2,11 ]. The methods described here are flexible enough to be applicable to any kind of potential involved and thus provide a useful tool for the calculation of Franck-Condon factor distributions.…”

“…Stieltjes histogram and Franck-Condon factor distribution according to formula(11) for calculations including 120 basis functions. In Figs.…”

“…Formula(11) has been used previously by G. W. F. Drake, Astrophys. J.184, 145 (1973) in connection with the calculation of spontaneous bound-free transition of the 2p 2 ape state of n-,…”

A multidisciplinary study on magnesium

“…47 Ten years later, he tried to improve the results employing 50 gaussians, the CI space was chosen to consist of roughly 500000 determinants, and the secular problem actually solved was of dimensions up to 10000. The smaller one consisted of 25 gaussians.…”