Ion-Pair Dissociation Dynamics of Cl₂ in the Range 13.26−13.73 eV Studied by Using XUV Laser and the Velocity Map Imaging Method

Abstract

The ion-pair dissociation dynamics of Cl2 in the range 13.26-13.73 eV have been studied employing coherent extreme ultraviolet radiation (XUV) and the velocity map imaging method. The Cl- (1S(0)) ion-pair yield spectrum has been measured, and 80 velocity map images of Cl- (1S(0)) have been recorded for the strong peaks in the spectrum. From the images, two dissociation channels corresponding to Cl- (1S(0)) + Cl+ (3P(j)) and Cl- (1S(0)) + Cl+ (1D(2)) have been found. The branching ratios among the fragments Cl+ (3P(0,1)), Cl+ (3P(2)), and Cl+ (1D(2)) and their corresponding anisotropy parameters beta have been determined. It is concluded that the ion-pair dissociation occurs via the predissociation of Rydberg states and its dynamics strongly depend on the excitation energies. The perpendicular and parallel transitions correspond to the excitation to two major Rydberg series converging to ion-core Cl2+ (A2Pi(u)), ...sigma(g)2pi(u)3pi(g)4[A2Pi(u)]ns sigma(g), 1Pi(u) (n = 6,7), and ...sigma(g)2pi(u)3pi(g)4[A2Pi(u)]nd pi(g), 1Sigma(u)+ (n = 4,5), respectively. For the production of fragments Cl+ (1D(2)), it is proposed that the perpendicular transitions are from the excitation to Rydberg states [A2Pi(u)]ns sigma(g), 1Pi(u) that is predissociated by ion-pair state 2 1Pi(u), while the parallel transitions are from the excitation to [A2Pi(u)]nd pi(g), 1Sigma(u)+ that interacts with ion-pair states 0(u)+ (1D(2)), 0(u)+ (3P(2)), and 0(u)+ (3P(0)).

Ion-Pair Dissociation Dynamics of SO2 in the Photon Energy Range 14.87−15.15 eV

“…8 The ion-pair dissociation usually occurs via the predissociation of Rydberg states; hence it carries rich information about the molecule superexcited states, and its mechanism has been studied in great detail in recent years. [8][9][10][11][12][13][14][15] Kratzat and co-workers have studied the ion-pair dissociation of SO 2 using the synchrotron radiation: 16 They recorded the Oion yield spectrum in the energy range 14-20 eV. 16 The peaks in the spectrum were tentatively assigned to Rydberg states converging to the C, D, E, and F states of the SO 2 + ion.…”

Dissociation dynamics of ion-pair states of Cl2at principal quantum numbers beyond 1500

“…Assuming that a homogeneous perturbation is responsible for the interactions, which is justified given that only the lowest rotational levels of Cl 2 are populated at the low temperature of the supersonic expansion (see also discussion in Refs. [18,19]), leads to the conclusion that the two Rydberg states and the ion-pair states are of 0 + u symmetry at short range and are thus accessible from the ground state in parallel electric-dipole transitions.…”

“…We report here on the observation of ion-pair states of Cl 2 which reveal the existence of such interactions. Cl 2 is an ideal system to study ion-pair states [11][12][13][14][15][16][17][18][19] because the very large electron affinity of the Cl atom makes it possible to observe these states over a wide energy range below the first dissociative ionization threshold. Moreover, Cl + possesses several low-lying electronic states, which offers the possibility, exploited in the present study, of studying interactions between different series of ion-pair states.…”

“…Zhou, Hao and Mo have also studied the ion-pair dissociation dynamics over a wide energy range above the lowest ion-pair dissociation threshold [18,19]. Compared to imaging studies of ion-pair dissociation continua, field ionization studies of bound ion-pair levels offer the advantages of being more precise and of providing additional, complementary information on the ion-pair levels, as will be shown subsequently.…”

Heavy Rydberg behaviour in high vibrational levels of some ion-pair states of the halogens and inter-halogens

“…This value is compatible with the extrapolation of the inner wall of the known part of the i.p. potential or ab initio calculations by Hao et al 25 for the ungerade i.p. states or Kokh et al; 26 the calculations of the latter for the β state extend to 80 000 cm −1 at r = 2.17 Å and point to r 0 ∼ 1.9-2.0 Å at the dissociation limit T ∞ = 96 094 cm −1 .…”