High resolution photoelectron spectrometry of negative ions: Rotational transitions in laser-photodetachment of OH?, SH?, SD?

Abstract

An apparatus for high resolution photoelectron spectrometry of negative ions is described. With this machine, energy spectra of electrons detached from OH , SH , and SD-ions by 488.0 nm and 514.5 nm radiation have been measured with a resolution of 5-7 meV. The rotational branches have been clearly resolved and the electron angular distributions have been determined for the different branches. The measured rotational structure has been reproduced in model calculations; for SH-, our results confirm the threshold model of Walker. The following rotational constants for the respective negative ions have been derived: B0(OH-)=18.75(15)c m 1, B0(SH )=9.39(3)cm 1, B0(SD-)=4.87(2)cm-1The electron affinities of SH, SD have been determined to be EA(SH)=2.317(2)eV and E A(SD) = 2.315 (2)eV; the negative ion vibrational frequencies have been found to agree with those in the parent neutrals to within about 100 cm-1

Partial cross sections for Rb? photodetachment in the region of the Rb(5p 2 P 1/2,3/2) thresholds and their analysis by multichannel quantum defect theory

“…The data points are shown with their statistical error bars, the smooth curve is a theoretical fit to the data based on (2), yielding the anisotropy parameter ]7=1.995 (5). The angular acceptance of the electron detector (EEA) and the small depolarization of the laser (<0.2 ~) have been taken into account as described in [6] Rb-.hv ~Rb.ecl: EXP. results.…”

“…8a) at which the angular distribution of the channel (I) electrons has been measured; a photon bandwidth of 0.6 cm-1 was used, except for the two runs close to the minima near 7"1/2 and T3/2, where the bandwidth was improved to 0.1 cm-L As an example, Fig. 6 shows the angular distribution data obtained at hv=16,499 cm -~ together with a fit calculation to determine the fl value as ]~=1.995(5) with a method described elsewhere in detail [6,10,14].…”

“…The experimental apparatus used for the present study has been recently described in some detail [6,10,11]. Here, we concentrate on the special aspects associated with the Rb-experiment.…”

“…Channel (I), also called the "elastic channel", yields fast electrons of 1.55-1.60 eV energy, which can be easily discriminated from the slow electrons resulting from channels (II) and (III [6] at T1/~=16,498.14(16 ) cm -1 [11], channel (III) appears at ~/2 = 16,735.74(16) cm-1. By a combination of electron spectroscopic studies and neutral Rb atom production measurements, we have determined accurate partial cross sections for the three channels as well as the total photodetachment cross section ato t (on a relative scale, resp.).…”

“…With the development of laser light sources, detailed photodetachment experiments have become possible [1][2][3][4]. The photon energy dependence of the cross section can be investigated with sub-meV resolution, and high quality photoelectron spectra can be recorded for virtually every negative ion with sufficient lifetime [4][5][6]. Electron scattering from A and photodetachment of A-lead to the same kind of final states.…”