The Au–Xe Ξ1/2–X2Σ+ (8–14, 0) progression as observed via (1 + 1) REMPI in (a) the [Au–Xe]+ parent ion mass channel, (b) the Xe+ mass channel, and (c) the Au+ mass channel (data from Ref. 2). The spectrum observed in the Xe+ mass channel has been multiplied by a factor of 2 relative to the [Au–Xe]+ channel for clarity.
VMI images recorded gating on (a) the Xe+ ions and (b) the Au+ following excitation of the same Ξ1/2–X 2Σ+ (10, 0) transition in Au−Xe at 41 581.8 cm−1. Observed central spots associated with nonresonant ionization of noncomplexed Au and Xe in the molecular beam have been removed for clarity.
The total kinetic energy release spectra extracted from the images in Fig. 2. The upper spectrum shows the TKER spectrum recorded in the Xe+ channel, while that recorded in the Au+ channel is shown by the below spectrum. Clearly, very different dissociation mechanisms are present in the two cases. Product channels 1–5 [blue online in (a)] show the predicted TKERs of the five accessible Xe+ product channels at the three-photon level. Only product channel 1 is not observed. Product channel 6 (red online) is assigned to single-photon dissociation of the molecular ion (see text).
(a) The TKER spectra extracted from the Xe+ images recorded following Au–Xe photolysis via the Ξ1/2–X 2Σ+ (9–13, 0) transitions. (b) TKER peaks as a function of the excitation photon energy. Channels 2–5 have a slope of 3 (blue online) representing the expected dependence for dissociation at the three-photon level, while channel 6 has a slope of unity (red online), corresponding to single-photon dissociation. The dashed line (blue online) shows a slope of 3 for comparison purposes. (c) The fractional contributions of three-photon dissociation signal in each of the product channels 2–5.
(a and b) The reconstructed Xe+ images observed following photolysis via the Ξ1/2 v ′ = 9 and 13 transitions, respectively, and (c) the extracted β 2 parameters. Channels 2–5 initially exhibit low or even negative β 2 parameters for v ′ = 9, evolving to larger (more positive) values with increasing photolysis wavenumber. This effect is clear in the very outer rings in the images in (a) and (b). Product channel 6 consistently shows an angular distribution of β 2 = 2, consistent with a strongly parallel single-photon dissociation. Observed central spots associated with nonresonant ionization of noncomplexed Xe in the molecular beam have been removed for clarity.
Summary of Au–Xe dissociation channels observed in the Xe+ channel. (Right) Excitation out of the Ξ1/2 state leads to direct ionization in a (1 + 1) REMPI process. Subsequent one-photon dissociation of the molecular cation [Au–Xe]+, generates Xe+ in channel 6. (Left) Excitation out of the Ξ1/2 state generates a superexcited Au–Xe** state which undergoes charge transfer, switching the ion core configuration to Au(5d 106s)–Xe+(5p 5) with the charge localized on the Xe. Absorption of a further photon leads to dissociative ionization at the three-photon level into Au + Xe+ product channels 2–5 as indicated.
Observed Xe+ product channels following the photolysis of Au–Xe via the Ξ1/2 v ′ = 10 state at 41 581.8 cm−1. Electron kinetic energy releases are predicted by energy balance calculations and reflect the Xe+ TKER peak widths at half maximum height. Uncertainties represent ± half width at the TKER peaks at half maximum.
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