Ab initio study of the ground and excited states of hydrogen sulphide using SCF and CI calculations

The absolute photoabsorption spectrum of ethylene oxide (C2H4O) has been measured between onset and 30 eV, using monochromated synchrotron radiation. Below the ionization threshold (10.56 eV) the spectrum is dominated by sharp peaks related to excitation of Rydberg series converging on the first ionization energy. Above the ionization threshold, valence-excited states, which give rise to broad bands, predominate. Underlying Rydberg states are signalled in weak vibrational structure on the valence bands. Ab initio multireference configuration interaction (MRDCI) calculations have been carried out to assist in assignment of the excited states, both valence and Rydberg. The lowest-lying valence state is electric-dipole forbidden; the first optically allowed valence state lies close to the ionization onset. The spectrum of the oxide is compared with those of cyclopropane (C3H6) and ethylene sulphide (C2H4S).

Section: Computational Detailsmentioning

confidence: 99%

The electronic states of ethylene oxide studied by photoabsorption andab initiomultireference configuration interaction calculations

Walker¹,

Holland²,

Shaw³

et al. 2008

“…The geometry of cyclopropane was fully optimized at the MP2 level using both cc-pVTZ and cc-pVDZ basis sets (Dunning 1989, Woon and Dunning 1993, 1994, Wilson et al 1999. The vertical excitation energy study was performed at the cc-pVTZ optimized equilibrium geometry using the cc-pVDZ basis set augmented with additional diffuse s-, p-and d-type functions (1s, 1p and 1d) functions (Guest and Rodwell 1976) which are placed at the centre of mass. All MRDCI calculations were performed in C 2v symmetry.…”

Section: Computational Detailsmentioning

confidence: 99%

The electronic states of cyclopropane studied by VUV absorption andab initiomultireference configuration interaction calculations

Walker

Holland

Shaw

et al. 2007

The absolute photoabsorption cross-section of cyclopropane has been measured between threshold and 30 eV using monochromated synchrotron radiation. The spectrum is dominated by prominent broad peaks arising from electronic transitions into valence-excited states. Much weaker structure ascribed to Rydberg states associated with excitation from the 3e or 1a 2 orbitals is also discernible. Some of these Rydberg states display vibrational progressions which can be correlated with similar structure observed in the corresponding photoelectron spectrum. Ab initio multireference configuration interaction calculations have been performed to obtain excitation energies for valence electron transitions into Rydberg or virtual valence orbitals. These theoretical predictions have enabled assignments to be proposed for most of the observed absorption bands.

“…The excited states of H2S, accessed by one-photon absorption, have also been the subject of several theoretical studies performed at various levels of sophistication (Shih et a1 1976, Guest and Rodwell 1976, Hatano 1978, Roberge and Salahub 1979, Rauk and Collins 1984, Diercksen and Langhoff 1987, Cacelli et a1 1988. At present, as a result of these experimental and theoretical efforts, most of the features of the electronic spectrum of H2S are basically understood, but there is still no general consensus on assignment of some Rydberg series, notably the 'B,(ns).…”

Section: Introductionmentioning

confidence: 99%

An ab initio study of multiphoton bound-bound electronic transitions of H₂S

Galasso

1989

Multiphoton absorption properties of H2S, transition probability coefficients and polarisation ratios are studied at ab initio level according to quantum electrodynamical methods, by employing RPA vertical excitation energies and transition moments and taking the random molecular orientation into account. The spectral observables associated with absorption of two, three and four photons with identical frequency and polarisation for the low-lying singlet excited states are reported. The concerted absorption of two or three photons with various polarisations from two laser beams is investigated as a function of the photon energies. The magnitude and direction of the electrochromic effects induced by a static external electric field on the molecular two-photon spectral properties are also analysed.