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Research Activities of EICO Users Group in 2002

• Si:2p site-specific excitation and fragmentation of bridged trihalosilyltrimethylsilyl molecules: Role of the bridge and final-state effect
• Site-specific fragmentation caused by core-level photoionization: Effect of chemisorption
• Ion desorption induced by core-level excitation of H₂O/Si(100): Evidence of desorption due to the multielectron excitation/decay

List of Publications

Research Activities in 1996 is here.

Research Activities in 1997 is here.

Research Activities in 1998 is here.

Research Activities in 1999 is here.

Research Activities in 2000 is here.

Research Activities in 2001 is here.

Si:2p site-specific excitation and fragmentation of bridged trihalosilyltrimethylsilyl molecules: Role of the bridge and final-state effect

S. Nagaoka, T. Fujibuchi, J. Ohshita, U. Nagashima, and I. Koyano
[Chem. Phys., 276, 243-256 (2002)]

To elucidate site-specific phenomena, we experimentally and computationally studied the spectroscopy and dynamics caused by Si:2p core-level photoexcitation of bridged trihalosilyl-trimethylsilyl molecules. We used the photoionization efficiency curve and the photoelectron photoion coincidence method to study the site-specific phenomena in the Si:2p photoexcitation of F₃SiCH₂CH₂CH₂Si(CH₃)₃, F₃SiCH=CHSi(CH₃)₃ and Cl₃SiC≡CSi(CH₃)₃ in the vapor phase. The site-specific excitation was revealed in the photoionization efficiency curves of all the molecules. The site-specific fragmentation is likely to be more evident when the distance between the two Si sites is large. For the site-specific fragmentation to be caused by the Si:2p photoexcitation, there should not be a C≡C bond between the atomic site of interest and any other near atomic site around which bond dissociation is undesirable. Not only initial-state effect but also final-state effect is likely to contribute to the occurrence of the different chemical shifts between the two Si sites of the bridged trihalosilyl-trimethylsilyl molecules.

Site-specific fragmentation caused by core-level photoionization: Effect of chemisorption

S. Nagaoka, K. Mase, A. Nakamura, M. Nagao, J. Yoshinobu, and S. Tanaka
[J. Chem. Phys., 117, 3961-3971 (2002)]

We used the energy-selected-photoelectron photoion coincidence (ESPEPICO) method to study site-specific fragmentation caused by C:1s photoionization of 1,1,1-trifluoro-2-propanol-d₁ (CF₃CD(OH)CH₃, TFIP-d₁) on a Si(100) surface. High-resolution electron energy loss spectroscopy showed that TFIP-d₁ is dissociatively chemisorbed like (CF₃)(CH₃)CDO-Si(100), and different chemical shifts at the three carbon sites were observed by photoelectron spectroscopy. The site-specific fragmentation evident in the ESPEPICO spectra of the sub-monolayer at room temperature indicates that the TFIP-d₁ there has an O-Si bond oriented in the trans position with respect to the C-CF₃ bond. Here we discuss the fragmentation processes in light of the results obtained with the ESPEPICO method and the Auger-electron photoion coincidence method.

Ion desorption induced by core-level excitation of H₂O/Si(100): Evidence of desorption due to the multielectron excitation/decay

S. Tanaka, K. Mase, S. Nagaoka, M. Nagasono, and M. Kamada
[J. Chem. Phys., 117, 4479-4488 (2002)]

This work is an investigation of the desorption by O1s excitation of ions from Si(100) reacted with water. Photoelectron, photostimulated desorption, and electron-ion coincidence spectroscopy are used to observe the process. When the incident photons have energy levels which are near the 1s threshold of O, they induce Auger decay that is accompanied by shakeup/off excitation and cascade Auger decay, and they are shown to be the main factor responsible for desorption in this case. When the photons have energy levels which are above the shakeup threshold, most of the desorption that occurs is a result of the shakeup excitation that accompanies the core excitation. In both cases, the desorption is induced by the respective multihole final states. The ion desorption yield for the two-hole final states of the normal process of Auger decay is small. The results are discussed, with the help of the Auger electron spectra, mainly in terms of the lifetime of the final state of Auger decay.