Ion-Pair Dissociation Dynamics of Cl₂: Adiabatic State Correlation

Abstract

The ion-pair dissociation dynamics of Cl2 -->(XUV) Cl(-)((1)S0) + Cl(+)((3P(2,1,0)) in the range 12.41-12.74 eV have been studied employing coherent extreme ultraviolet (XUV) radiation and the velocity map imaging) method. The ion-pair yield spectrum has been measured, and 72 velocity map images of Cl(-)((1)S0) have been recorded for the peaks in the spectrum. From the images, the branching ratios among the three spin-orbit components Cl(+)((3)P2), Cl(+)((3)P1) and Cl(+)((3)P0) and their corresponding anisotropic parameters beta have been determined. The ion-pair dissociation mechanism is explained by predissociation of Rydberg states converging to ion-core Cl2(+)(A(2)Pi(u)). The Cl(-)((1)S0) ion-pair yield spectrum has been assigned based on the symmetric properties of Rydberg states determined in the imaging experiments. The parallel and perpendicular transitions correspond to the excitation to two major Rydberg series, [A(2)Pi(u)]3d pi(g), (1)Sigma(u)(+) and [A(2)Pi(u)]5s sigma(g), (1)Pi(u), respectively. For the production of Cl(+)((3)P0), it is found that all of them are from parallel transitions. But for Cl(+)((3)P1), most of them are from perpendicular transitions. The production of Cl(+)((3)P2) is the major channel in this energy region, and they come from both parallel and perpendicular transitions. It is found that for most of the predissociations the projection of the total electronic angular momentum on the molecular axis (Omega) is conserved. The ion-pair dissociation may be regarded as a probe for the symmetric properties of Rydberg states.

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

“…The superexcited molecule decays in various channels: autoionization, dissociative ionization, neutral dissociation, and ion-pair dissociation . 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. − …”

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.…”

Halogens and noble gases

“…A recent study of the ion-pair dissociation dynamics of Cl 2 has been undertaken using coherent extreme UV (XUV) radiation and the velocity map imaging method. 28 Anisotropic parameters for the three spin-orbit components and their branching ratios were determined. A thorough discussion of the predissociation mechanism of Ryberg states provides insight into the observed ion-pair dissociation dynamics.…”