下條 竜夫

Abstract The primary and secondary fragmentation dynamics of iodobenzene following its ionization at 120 eV were determined using three-dimensional velocity map imaging and covariance analysis. Site-selective iodine 4d ionization was used to populate a range of excited polycationic parent states, which primarily broke apart at the carbon-iodine bond to produce I⁺ with phenyl or phenyl-like cations (C _n H or C _n H , with n  =  1 – 6 and x  =  1 – 5). The molecular products were produced with varying degrees of internal excitation and dehydrogenation, leading to stable and unstable outcomes. This further allowed the secondary dynamics of intermediates to be distinguished using native-frame covariance analysis, which isolated these processes in their own centre-of-mass reference frames. The mass resolution of the imaging mass spectrometer used for these measurements enabled the primary and secondary reaction channels to be specified at the level of individual hydrogen atoms, demonstrating the ability of covariance analysis to comprehensively measure the competing fragmentation channels of aryl cations, including those involving intermediate steps.

The dissociation dynamics of UV pumped iodothiophene molecules are investigated using velocity map ion imaging, in combination with site-selective extreme ultraviolet ionization of the iodine atom.

近年、真空中での溶液あるいは液体状態の分光が注目され、水（液体）、アルコール（液体）、溶液の光電子スペクトル、軟Ｘ線発光スペクトル、内殻吸収スペクトルなどが測定されてきた。本研究では超音波振動による微少液滴生成技術を利用し、水溶液内のアミノ酸の軟Ｘ線吸収スペクトル測定を試みた。その結果、軟Ｘ線領域では、液滴の窓への付着、超音波噴霧の不安定性により、十分なＳ／Ｎ測定には、様々な改良が必要なことがわかった。

炭酸分子の酸素1s、炭素1sしきいエネルギー領域の吸収スペクトル測定を光電子-光イオン-光イオン同時測定法を利用して行った。得られたスペクトルには1s→π*由来と考えられるピークがあらわれたが、水および二酸化炭素の単体分子からのシグナルによる寄与がきわめて大きく、炭酸分子由来のシグナル強度も弱かったため、明確なピーク位置は確定することはできなかった。

We have realized element-specific pump-probe time-resolved hard X-ray photoelectron spectroscopy (TR-HAXPES) for the study of ultrafast electron dynamics in condensed matter. TR-HAXPES has been applied for the first time to determine the temporal evolution of space-charge effects on Ti 1s core-level photoelectron spectra of SrTiO₃ at the SACLA X-ray free electron laser facility. We found that the temporal evolution of Ti 1s kinetic energy shifts can be well explained by a mean-field model for the electron propagation in the vacuum. We also report preliminary results of a real-time laser-assisted valence-transition in YbInCu₄, observed by measuring Yb 3d_5/2 core-level HAXPES spectra at BL19LXU of SPring-8, under ON/OFF conditions of an optical pump-laser. We observed drastic changes in intensities of the Yb²⁺ and Yb³⁺ spectral components induced by pump-laser irradiation.