The assignment of the Rydberg transitions in the electronic absorption spectrum of formaldehyde
- 1 May 1977
- journal article
- research article
- Published by AIP Publishing in The Journal of Chemical Physics
- Vol. 66 (9), 3908-3916
- https://doi.org/10.1063/1.434467
Abstract
The electronic spectra of H2CO, D2CO, HDCO, and D2 13CO have been recorded between 1250 and 2000 Å and the vibrational fine structure associated with the n→3s, 3p x , 3p y , 3p z , 3d transitions assigned. The electronic origin bands in the Rydberg transitions show quite unusual isotope effects, with the ν (D2CO) –ν (H2CO) shift for the n→3d transition being somewhat smaller than the limiting value of the ion while the lower energy n→3s and 3p y transitions have anomalously large values. As these effects cannot be accommodated by the changes in the totally symmetric in‐plane frequencies on excitation, they are attributed to large differences in ν5 and ν6 in the upper and lower electronic states. Direct information concerning the reduction in ν6 on excitation comes from the identification of a series of low frequency bands in the n→3p y system of D2CO which were assigned to quanta in ν6. The potential function which was derived from this data was found to be very anharmonic and could contain a double minimum. The reduction in V (Q 6) at large Q 6 was attributed to a coupling between the Rydberg1 A 1(n, 3p y ) state and a second 1 B 2 state which lies at higher frequencies. An estimate of the coupling between these states lead to a value of 1480 cm−1 for the vibronic matrix element. While this value is entirely compatible with what would be expected for valence–valence coupling, it is somewhat larger than what would have been anticipated for vibronic coupling between Rydberg states.Keywords
This publication has 18 references indexed in Scilit:
- Study of cross sections, oscillator strengths, generalized oscillator strengths, and atomiclike character of the molecular orbitals of formaldehyde for inelastic transitions to valence and Rydberg statesThe Journal of Chemical Physics, 1975
- Ultraviolet spectra and excited states of formaldehydeChemical Reviews, 1975
- The lower rydberg states of formaldehydeChemical Physics Letters, 1974
- Rydberg states of polyatomic molecules using model potentialsThe Journal of Chemical Physics, 1974
- Remarks on the Description of Excited Electronic States by Configuration Interaction Theory and a Study of the (π → π*1) State of H2COThe Journal of Chemical Physics, 1972
- Photoionization and Absorption Spectrum of Formaldehyde in the Vacuum UltravioletThe Journal of Chemical Physics, 1971
- Calculation of the electronic spectrum of formaldehydeChemical Physics Letters, 1971
- Combined SCF and CI Method for the Calculation of Electronically Excited States of Molecules: Potential Curves for the Low-Lying States of FormaldehydeThe Journal of Chemical Physics, 1970
- Configuration Interaction Studies of Ground and Excited States of Polyatomic Molecules. I. The CI Formulation and Studies of FormaldehydeThe Journal of Chemical Physics, 1969
- The Far Ultraviolet Absorption Spectra of Formaldehyde and the Alkyl Derivatives of H2O and H2SThe Journal of Chemical Physics, 1935