- Dissociation dynamics of CH4+ core ion in the 2A1 state
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Threshold-photoelectron photoion coincidence (TPEPICO) spectra of CH4 have been observed with synchrotron radiation at the excitation to the 2A1 (υ1=0-3) ionic states as well as to the 4pt2 Rydberg (υ1 = 0-4) states.In all the TPEPICO spectra observed, the CH3+ band shape was almost rectangular, which suggests that the translational and internal energy distributions of CH3+ are very narrow.The total kinetic energy releases (KERs) have been estimated from the CH3+ band shape.As a result, it was found that the CH3+ species were in an electronically excited state.There was a narrow distribution of the total KERs and similarity in the TPEPICO CH3+ band shapes between the spectra at the 2A1 ionic state and the 4pt2 Rydberg state excitations, which led to the conclusion that the Rydberg electron is just a spectator and the dissociation of the core ion plays an important role in dissociation through the 4pt2 Rydberg state.Similar results have also been obtained for CH2+ and CH+ productions.However, on the other hand, an H+ fragment has been observed only at the 2A1 state excitation.It showed a band with a long tail in the slower flight time region.The total average KERs and the decay rates have been estimated from band shape simulation.From these results, it has been found that a dissociation limit of the H+ ion exists just below the 2A1 ionic state.The dissociation mechanisms through the 4pt2 Rydberg state have been discussed in detail in comparison with those of the 2A1 ionic state.
- Furuya, Kenji,Kimura, Katsumi,Sakai, Yasuhiro,Takayanagi, Toshinobu,Yonekura, Nobuaki
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p. 2720 - 2728
(2007/10/02)
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- Reactions of He+, Ne+, and Ar+ with CH4, C2H6, SiH4, and Si2H6
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The rate coefficients and product-ion distributions for the reactions of He+ and Ar+ with silane and disilane have been measured in a drift tube, typically for collision energies of 0.01-1 eV.The total charge-exchange rate coefficients are found to be roughly independent of E/N, or collision energy, and are about equal to the Langevin values for the reactions of He+ with SiH4 and C2H6 and Ar+ with CH4 and C2H6.The He+ rate coefficients on CH4 and Si2H6, and the Ne+ rate coefficients on SiH4 and Si2H6 are 50percent to 80percent of the Langevin values, while the Ar+ rate coefficients on SiH4 and Si2H6 are much smaller.Product ions tend to be hydrogen poor with very infrequent breaking of the C-C or Si-Si bonds.Furthermore, hydrogen stripping is more severe for the silanes than the alkanes.These product-ion distributions bear no resemblance to the product-ion distributions of either photoionization or electron collisional ionization.
- Chatham, H.,Hils, D.,Robertson, R.,Gallagher, A. C.
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p. 1301 - 1311
(2007/10/02)
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