Rotational state selective photoionization of the H2 molecule from B 1Σ+u(v ′=0,3) states

Abstract

Selective photoionization from single rotational states of the B 1Σ+u(v′=0 and 3) excited state of the H2 molecule has been investigated with fixed frequency and tunable laser radiation around λ=266 nm. State selection of the B-state levels was achieved by tunable VUV laser excitation around λ=110 and 106 nm, respectively. The ionization cross section has been determined for different states, and found to be critically dependent upon the initial rotational quantum state and to show pronounced spectral structure with the ionization wavelength. At λI=266.05 nm the cross section varies between 0.23×10−18 and 1.2×10−18 cm2, depending on the initial state.

Photoionization cross sections of rovibrational levels of the B 1Σ+u state of H2

“…The results are presented in Table I together with the experimentally deduced cross sections of Ref. 11. The agreement between the length and the velocity forms of cross sections indicates that the single determinant description of the B state as well as of the photoelectron continuum is sufficiently accurate.…”

“…11 The theoretical values are consistently higher than the experimental ones. Our calculations have not included autoionization.…”

“…We believe that such effects could have influenced the results of Meier eta/. 11 In the following section we address these questions.…”

“…These cross sections were extracted by observing the saturation behavior of the ion signal as the intensity of the ionizing laser is varied in their two color ( 1 + 1) REMPI experiment. We have calculated the relevant cross sections using ab initio electronic wave functions and our calculated values are compared with the measured ones 11 in Table I. The experimental values seem to be consistently lower than the theoretical numbers by about an order of magnitude.…”

“…21 Since Meier et a/. 11 collected total ion signals, we have summed the cross sections over the symmetry allowed ionic rotational states and energetically allowed ionic vibrational states. The results are presented in Table I together with the experimentally deduced cross sections of Ref.…”