Theoretical study of the vibrational structure of the 1(n,π*) transition in diimide: potential curves and Franck–Condon analysis

1977 ◽  
Vol 55 (9) ◽  
pp. 1533-1545 ◽  
Author(s):  
M. Perić ◽  
R. J. Buenker ◽  
S. D. Peyerimhoff
Keyword(s):  
Band Structure ◽  
Excited States ◽  
Electronic Transition ◽  
Isotope Shift ◽  
Theoretical Study ◽  
Vibrational Structure ◽  
Absorption System ◽  
Electronic Transition Moment ◽  
Franck Condon ◽  
Potential Curves

Ab initio CI potential curves are reported for the ground and 1(n,π*) excited states of diimide for each of the six possible internal coordinates. These results are then used to obtain vibrational wavefunctions and frequencies for both states, which in turn are combined with electronic transition moment data to allow a Franck–Condon analysis of the band structure of the (dipole-forbidden) n–π* absorption system. This procedure allows one to reproduce the main features of the observed spectra of N2H2 and N2D2 and indicates that the majority of the vibrational transitions seen are vibronically induced via the antisymmetric NH stretching mode v5. The calculations are in essential agreement with the earlier experimental interpretation of the vibrational structure of this transition in terms of progressions in the symmetric bending (v2) and NN stretching (v3) frequencies, except that they indicate that the previous v2′ numbering should be altered by three units. According to this interpretation the isotope shift for the vibronic origin is 672 cm−1 compared with the corresponding calculated value of 666 cm−1. It is argued that several other weaker transitions seen experimentally arise via a different inducement mechanism, namely the torsion (v4) mode, and as such are only observed in energy regions where v5-induced transitions cannot occur.

AN EXPERIMENTAL STUDY OF THE BAND INTENSITIES IN THE CN RED SYSTEM

1958 ◽  
Vol 36 (1) ◽  
pp. 127-133 ◽  
Author(s):  
R. N. Dixon ◽  
R. W. Nicholls
Keyword(s):  
Experimental Study ◽  
Carbon Tetrachloride ◽  
Electronic Transition ◽  
Transition Moment ◽  
Active Nitrogen ◽  
Electronic Transition Moment ◽  
System A ◽  
Condon Factors ◽  
Franck Condon

Experimental band intensities in the CN red system, A (2Πi) →X(2Σ+), have been measured using an active nitrogen – carbon tetrachloride source. Using calculated Franck–Condon factors qν′ν″ the electronic transition moment Re(r) is found to vary little over the range 1.04 < r < 1.27 Å.

Variation of the Electronic Transition Moment and the Effective Vibrational Temperature in 4800–6700-Å System of MnO Molecule

1971 ◽  
Vol 25 (5) ◽  
pp. 554-556
Author(s):  
Prem Shankar Dube ◽  
A. K. Chaudhry ◽  
G. D. Baruah ◽  
D. K. Rai
Keyword(s):  
Electronic Transition ◽  
Vibrational Temperature ◽  
Transition Moment ◽  
Electronic Transition Moment ◽  
Straight Line ◽  
Condon Factors ◽  
Effective Vibrational Temperature ◽  
Franck Condon ◽  
Photographic Photometry

The 4800–6700-Å system of MnO has been excited in an arc. Using the photographic photometry, the relative band intensities have been measured. The data were interpreted with the aid of Franck-Condon factors and r centroids. The electronic transition moment is found to vary according to the relation Re(r) = const (1- 3.192 r + 1.99 r2), where 1.736≤ r≤ 1.90 Å. The slope of the straight line plot of log ∑ v″ I/v4 against G'(ν') for ν' progression gives an estimate of effective vibrational temperature to be 3860 K.

The visible band systems of GeH+ and GeD+ in the helium afterglow

1986 ◽  
Vol 64 (10) ◽  
pp. 1374-1378 ◽  
Author(s):  
Sumio Yamaguchi ◽  
Masaharu Tsuji ◽  
Yukio Nishimura
Keyword(s):  
Electronic Transition ◽  
Transition Moment ◽  
Spectroscopic Constants ◽  
Electronic Transition Moment ◽  
Visible Band ◽  
Condon Factors ◽  
First Time ◽  
Franck Condon ◽  
Morse Potentials ◽  
Higher Sensitivity

The [Formula: see text] intercombination bands of GeH+ and GeD+ have been observed from the helium afterglow reactions of GeH4 and GeD4, respectively. Only the (0,0) band of [Formula: see text] had been rotationally analyzed before; the higher sensitivity of the new measurements made possible the rotational analyses of four weaker bands. Eleven bands of [Formula: see text] were observed for the first time, and rotational analyses were made of five dominant bands. By using isotope relationships, we obtained detailed spectroscopic constants for the [Formula: see text] and X1Σ+ states of GeH+ and GeD+. Franck–Condon factors and r centroids of the [Formula: see text] transitions of GeH+ and GeD+ have been calculated on the basis of Morse potentials. The dependence of the electronic transition moment on the r centroid and the relative vibrational populations of [Formula: see text] and [Formula: see text] have been estimated.

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

1977 ◽  
Vol 55 (20) ◽  
pp. 3664-3675 ◽  
Author(s):  
M. Perić ◽  
S. D. Peyerimhoff ◽  
R. J. Buenker
Keyword(s):  
Excited States ◽  
Band System ◽  
Vibrational Structure ◽  
Electronic Transitions ◽  
Dissociation Limit ◽  
Potential Surfaces ◽  
Double Zeta ◽  
Polarization Functions ◽  
Franck Condon ◽  
Ci Calculations

Ab initio SCF and CI calculations for the potential surfaces of HCN in ground and various 1(π,π*) excited states are carried out using an AO 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 [Formula: see text] band system is the 1∑−−1A″species, and not the 1Δ as originally believed. In addition a detailed mechanism for the observed predissociation of the α state is outlined, in which the gradual conversion of the π* MO of bent HCN into a pure hydrogenic 1s AO plays a key role. Arguments are also presented in favor of assigning the [Formula: see text]transition seen in DCN to a 1Δ-21A′ upper state with the same D + CN dissociation limit as for the 1∑−−1A″ species.

Sign in / Sign up

Export Citation Format

Share Document