Fully relativistic calculations on the potential energy surfaces of the lowest 23 states of molecular chlorine

Abstract

The electronic structure and spectroscopic properties (Re, ωe, ωexe, βe, and Te) of the ground state and the 22 lowest excited states of chlorine molecule were studied within a four-component relativistic framework using the MOLFDIR program package. The potential energy curves of all possible 23 covalent states were calculated using relativistic complete open shell configuration interaction approach. In addition, four component multireference configuration interaction with single and double excitation calculations were performed in order to infer the effects due to dynamical correlation in vertical excitations. The calculated properties are in good agreement with the available experimental data.

A complete quantum mechanical study of chlorine photodissociation

“…Finally, in 2008 a set of all 23 states corresponding to the production of two Cl( 2 P) atoms were calculated, using a complete open shell configuration interaction approach. 2 Although calculated in a way that was unsuitable for the present quantum mechanical (QM) dynamical study, agreement in the spectroscopic quantities calculated for these potentials and the ones of Kokh et al presented in Ref. 32 is extremely good.…”

“…We defer detailed comparison with experimental data to the accompanying paper, 16 suffice it to say that the agreement between the calculations and the available experimental results is generally very good. The calculations slightly underestimate the incoherent a (2) 0 (⊥) parameter, and overestimate the coherent parameter a (2) 2 (⊥), suggesting that the calculation might slightly underestimate the non-adiabatic effects in the dissociation.…”

“…The correction factors employed in the space fixed frame are shown in Table X. Although the correction factors are quite close to unity, and the effects of non-axial recoil therefore relatively small, the inclusion of this rotational smearing tends to bring the experimental and simulated data into slightly better agreement, although discrepancies with a (2) 0 (⊥) at longer wavelengths remain significant.…”

“…The top panel of Fig. 13 shows the coherent Re[a (2) 1 ( , ⊥)] alignment parameter for fragment from the (Cl + Cl*) channel, and shows that the alignment, as well as the orientation, could be expected to be non-zero and highly oscillatory with photon energy. The dynamical calculations indicate that three different states are involved in the photodissociation to the excited channel, meaning that five different quantities (three magnitudes and two phase differences) are required to fully characterize the dynamics of this channel, and the determination of the excited state alignment would be a necessary part of this.…”

“…Considered to be a vital component in the mechanism of ozone depletion, 1 Cl 2 is one of the ten most produced chemicals in industry. 2 It has also been a testing ground for the development of new techniques, [3][4][5][6][7] providing the basis for several ground-breaking studies on photofragment polarization, 5,8,9 in particular the first paper to link the fully quantum mechanical expressions of Siebbeles et al 10 to ion imaging. 5 Much easier to study experimentally than hydrogen or fluorine, yet still sufficiently simple to be amenable to detailed theoretical studies, Cl 2 photodissociation has been the target of several high level potential energy surface calculations and, crucially, of angular momentum polarization studies over a range of wavelengths throughout its UV absorption spectrum.…”