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

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−(1S0) ion-pair yield spectrum has been measured, and 80 velocity map images of Cl−(1S0) have been recorded for the strong peaks in the spectrum. From the images, two dissociation channels corresponding to Cl−(1S0) + Cl+(3P j ) and Cl−(1S0) + Cl+(1D2) have been found. The branching ratios among the fragments Cl+(3P0,1), Cl+(3P2), and Cl+(1D2) and their corresponding anisotropy parameters β 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 +(A2Πu),...σg 2πu 3πg 4[A2Πu]nsσg, 1Πu (n = 6,7), and...σg 2πu 3πg 4[A2Πu]ndπg, 1Σu +(n = 4,5), respectively. For the production of fragments Cl+(1D2), it is proposed that the perpendicular transitions are from the excitation to Rydberg states [A2Πu]nsσg, 1Πu that is predissociated by ion-pair state 21Πu, while the parallel transitions are from the excitation to [A2Πu]ndπg, 1Σu + that interacts with ion-pair states 0u +(1D2), 0u +(3P2), and 0u +(3P0).