Rotationally Resolved Photoelectron Asymmetry Parameter of H₂Using Ne-I 736Å Radiation

The effect of vibrational autoionization on the H2+X2Σg+state rotationally resolved photoionization dynamics

“…H 2 + X 2 g + v + , N + state photoelectron angular distributions were first investigated experimentally using NeI and HeI resonance radiation [50][51][52][53][54][55][56][57][58] and the results from the various studies were in general agreement that at an excitation energy of 21.2 eV the anisotropy parameters for the individual transitions within the Q-branch all lie close to 2. For example, the recent measurements of Öhrwall and Baltzer [58] give β(Q-branch) = 1.86, 1.86, 1.85 and 1.85 for v + = 0, 1, 2, 3, respectively, whilst the earlier measurements of Ruf et al [53] gave β(Q-branch) > 1.9 at hν = 16.66, 16.85 and 21.2 eV.…”

“…At hν = 21.2 eV, Pollard et al [52] report β(S-branch) = 0.87 for the v + = 0 level, whilst Ruf et al [53] obtained values ranging between 0.65 and 0.81 for the v + = 0 to 5 levels. At hν = 16.67 eV, Pollard et al [52] measured β(S-branch) = 0.08 for the v + = 0 level, whereas, for the same level, Takahashi et al [55] obtained 0.66. Ruf et al [53] measured values ranging between 0.47 and 0.62 for the v + = 0 to 3 levels and, at hν = 16.85 eV, reported β(S-branch) = 0.76 for the v + = 0 level.…”

“…Rotationally resolved X 2 g + state photoelectron spectra have been measured previously using NeI (hν = 16.66, 16.85 eV) [50][51][52][53][54][55] and HeI (hν = 21.2 eV) [50,[52][53][54][56][57][58] resonance radiation. These spectra, which arise from direct ionization, exhibit an intense Q (N + -N = 0) and a much weaker S (N + -N = 2) branch.…”

Synchrotron radiation excited photoelectron spectrum of with rotational resolution

“…The uncertainty in angle may introduce a β dependence of the rotational branching ratio. It is known from angle-resolved studies that Q ( N = 0) and S ( N = 2) branches differ in β value [5,7,8,10,11]. According to the recent measurements of Öhrwall and Baltzer [5], the β value at hν = 21.218 eV is ≈1.8 for the Q branch, and ≈ 0.5-0.8 for the S branch for v = 0-3.…”

“…In an attempt to obtain more information on the photoionization of H 2 , we have recorded a rotationally resolved photoelectron spectrum with synchrotron radiation (hν = 27 eV), to find out the rotational branching ratio. The rotational structure has been studied with resonance lamp excitation by a number of authors [5][6][7][8][9][10][11]. A wavelength dependence has already been seen for the rotational branching ratio in these spectra; the S-branch ( N = 2) has higher relative intensity when excited with He I (λ = 584 Å) than with Ne I (λ = 736 Å) radiation.…”