| Summary |
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.
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