Site-specific fragmentation in condensed (CH3S)2 by sulfur K-edge photoexcitation

Abstract

Rotational population distribution of KH (v=0, 1, 2, and 3) in the reaction of K(52 P J , 62 P J , and 72 P J ) with H2: Reaction mechanism and product energy disposalThe site-specific fragmentation by core-to-valence resonant photoexcitation has been investigated for condensed ͑CH 3 S͒ 2 ͑dimethyl disulfide͒. The data presented are the desorption yields of the fragment ions from multilayered ͑CH 3 S͒ 2 around the sulfur K-edge photoexcitation as well as the x-ray absorption and Auger decay spectra. The x-ray absorption spectrum exhibits the double structure of the S 1s→* resonance peak corresponding to the S 1s→*͑S-S͒ and S 1s→*͑S-C͒ photoexcitations. It was found that the S 1s→*͑S-C͒ excitation is predominantly followed by the CH 3 ϩ desorption, but the CH 3 ϩ and S ϩ ions are desorbed in comparable intensity at the S 1s→*͑S-S͒ excitation. The Auger decay spectra around the S 1s→* excitation revealed that there exist two kinds of sulfur KL 2,3 L 2,3 spectator Auger decay originating from the S 1s→*͑S-S͒ and S 1s→*͑S-C͒ resonant excitations. The observed site-specific fragmentation is interpreted in terms of the localization of the spectator electron in each antibonding orbital, i.e., *͑S-S͒ and *͑S-C͒.

Photon stimulated ion desorption from poly(3-methylthiophene) following sulphur K-shell excitation

“…Further evidence of the ASID mechanism comes from the comparison of the edge-jump ratios (Table 1), which shows that the ion yield curve for S 2þ is different from the photoabsorption one. Probably the Auger decay process is more complex and similar to the process described by Baba et al in the fragmentation study of condensed (CH 3 S) 2 by sulphur K-edge photoexcitation [31].…”

“…On the contrary, in the case of S þ , the XESD process did not produce any S þ desorption above and below the sulphur K-shell region, or at least the probability of its formation was below the detection limit. Therefore, S þ desorption is mainly formed by an Auger-stimulated process in which a direct or more complex decay process like a K-LL Auger process followed by a double L-VV could be involved [31].…”

“…Specifically, in the study of OCS photofragmentation at the S K-edge [32], it was found that the formation of S 3þ and S 4þ branching ratios increase with the onset of S 1s excitation and ionization, being higher above the ionization threshold. In addition, in the PSID study of condensed (CH 3 S) 2 [31], final electronic configurations having four holes in valence orbitals were assigned for all excitations. The above high accumulation of positive charges in valence orbitals would favour the Coulomb explosion mechanism increasing simultaneously the probability of desorption of multiple charged ions.…”

Breaking the disulfide chemical bond using high energy photons: the dimethyl disulfide and methyl propyl disulfide molecules

“…Our spectrum shows an overall agreement with previous gas phase results obtained by Hitchcock et al 9 as well as with the condensed phase measurements made by Baba. 10 The rst structure in the spectrum is composed by two main s resonances, observed at 2470.9 eV and 2471.8 eV while a broad shape resonance is observed around 2480 eV. These energy values are in very good agreement with the recent values obtained by Pickering et al 11 Our theoretical results for the DMDS S 1s photoabsorption, obtained at IS-MRMP with aug-ccpCVDZ/DKH3 show an excellent numerical agreement with the experimental data and conrms that the rst peak in the experimental spectrum can be attributed to a transition to a s* (S-S) orbital while the second peak corresponds to a transition to a s* (S-CH 3 ) orbital.…”

State-Specific Enhancement ofCl+andCl−Desorption forChen1, Lu2 2001Phys. Rev. Lett.

“…In addition, the core electrons of a specific element in a molecule can be selectively excited into specific valence orbitals and Rydberg states below the ionization threshold. In the past decade, site-selective fragmentation via core-level excitation was observed in gaseous molecules [1,2], molecular adsorbates on surfaces [3][4][5][6], and polymers [7]. However, some molecules, such as Fe͑CO͒ 2 ͑NO͒ 2 , showed no site selectivity after excitations of core electrons of different sites [8], and no selectivity was found for Si 2 ͑CH 3 ͒ 6 after transitions from Si͑2p͒ electrons into various resonances [9].…”