分子科学研究所　研究棟201セミナー室

Recent developments of single-photon vacumm ultraviolet (VUV) and two-color infrared (IR)-VUV and VUV-IR photoionization and photoelectron methods for spectroscopy and reaction dynamics studies will be presented. [1-7] The application of the VUV pulsed field ionization (PFI) methods has allowed the determination of thermochemical data of many small molecules with unprecedented precision. By preparing molecules in single rovibrational states using a single-mode IR laser (optical resolution = 0.007 cm-1) prior to VUV photoionphotoelectron measurements, we have demonstrated that rotationally selected and resolved IRVUV-PFI-photoelectron (PFI-PE) spectra for polyatomic molecules can be obtained. Using VUV photoionization as a probe and by scanning the IR laser frequency, we have shown that high resolution IR spectra for many neutral polyatomic species can be measured with high sensitivity. Two-color VUV-IR photo-induced Rydberg ionization experiment, in which high-n Rydberg states are prepared by VUV-photoexcitation followed by IR-induced autoionization, has also been found to be applicable for IR spectroscopic measurement of molecules in excited Rydberg states. High-n Rydberg tagging time-of-flight measurements for nascent H, O, and S atomic fragments formed in laser photodissociation have been successfully made using single-photon VUV　excitation.

References:
1. C. Y. Ng, “Vacuum Ultraviolet Spectroscopy and Chemistry Using Photoionization and Photoelectron Methods”, Ann. Rev. Phys. Chem. 53, 101-140 (2002).
2. C. Y. Ng, “State-Selected and State-to-State Ion-Molecule Reaction Dynamics”, J. Phys. Chem. A (Feature Article), 106, 5952-5966 (2002).
3. C. Y. Ng, “Two-Color Photoionization and Photoelectron Studies by Combining Infrared and Vacuum Ultraviolet”, J. Electron Spectroscopy & Related Phenomena (invited review), 152, 142-179 (2004).
4. Rainer A. Dressler, Y. Chiu, D. Lavandier, X. N. Tang, Y. Hou, C. Chang, C. Houchins, H. Xu, and Cheuk-Yiu Ng, “The Study of State-Selected Ion-Molecule Reactions using the Pulsed-Field Ionization-Photoion Technique”, J. Chem. Phys. 125, 132306 (2006).
5. Kai-Chung Lau and Cheuk-Yiu Ng, “Benchmarking state-of-the-art ab initio thermochemical predictions with accurate pulsed-field ionization photoion-photoelectron measurements”, Accounts on Chemical Research, 39, 823-829 (2006).
6. B. Jones, J. Zhou, L. Yang, and C. Y. Ng, “High-resolution Rydberg tagging time-offlight measurements of atomic photofragments by single-photon vacuum ultraviolet Laser Excitation”, Rev. Sci. Instrum. 79, 123106 (2008).
7. C. Y. Ng, “Spectroscopy and Dynamics of Neutrals and Ions by high-resolution infraredvacuum ultraviolet photoionization and photoelectron methods”, in “Frontiers of Molecular Spectroscopy”, edited by Jaan Laane (Elsvier, 2009) Chap. 19, page 659-691.

来月の6月10-11日（水・木）にカリフォルニア大学デービス校の Cheuk Ng 教授が所長招聘で分子研に来られます。原子分子やvｄWクラスターの光イオン化質量分析と光電子分光研究の権威で、光イオン化や光電子脱離の教科書の著者 や総説集の編者としても知られています。今回は化学反応討論会の招待講演者として来日され、所長招へいで岡崎に立ち寄られることになりました。この機会 に、６月11日午後4時からオープンセミナーをお願いしました。赤外レーザーで単一振動回転状態に励起された多原子分子の真空紫外光電子分 光の研究を紹介されます。ポンプの赤外光励起はもちろん、プローブの真空紫外イオン化でもパルス電場法で回転線分離がなされており、２色励起による超高分 解能の赤外分光が達成されているという話題です。細部の話ではなく、仕事全体の概観を紹介されるとのことですので、皆様どうぞお気軽にご出席ください。

見附孝一郎 （光分子科学研究領域）