High-resolution pulsed-field ionization photoelectron spectroscopy using multi-bunch synchrotron radiation

Technical Report · Tue Apr 01 04:00:00 EST 1997

DOI:https://doi.org/10.2172/604271· OSTI ID:604271

Hsu, C. W. ^[1]; Evans, M.; Ng, C. Y. ^[2]; Heimann, P. ^[3]

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1. Lawrence Berkeley National Lab., CA (United States)
2. Ames Lab., IA (United States)
3. Ernest Orlando Lawrence Berkeley National Lab., CA (United States)

BL9.0.2.2 is the newly constructed experimental End Station 2 at the Chemical Dynamics Beamline 9.0.2 of the Advanced Light Source (ALS). It is dedicated to the high resolution photoionization study of molecules of interest to atmospheric and combustion chemistry. This End Station is equipped with a high resolution scanning monochromator, which has been demonstrated to have a world record resolution of E/{delta}E=70,000. Taking the advantage of the high resolution ALS light, the authors have improved the energy resolution in threshold photoelectron spectroscopy (TPES) to 0.8 meV. The TPES is a popular technique for photoionization experiments at all synchrotron radiation facilities due to its high energy resolution as compared to that of traditional photoelectron spectroscopy (PES). TPES achieves higher energy resolution by preferentially detecting near zero kinetic energy photoelectrons resulting from threshold photoionization. However, the spectra obtained from the TPES technique generally are complicated by the simultaneous detection of electrons with nonzero kinetic energy, which are not fully discriminated against. On the other hand, the spectra obtained from pulsed field ionization photoelectron spectroscopy (PFI-PES) are completely free of the contamination from kinetic electrons. The PFI-PE technique basically involves the detection of the photoelectrons from field ionization of the very high-n Rydberg states, a few cm{sup {minus}1} below the ionization energy (IE), by applying a delayed pulsed electric field. Within a delay of a few microseconds, all the prompt electrons formed from direct ionization will escape from the photoionization region and will not be collected. The authors have recently overcome problems with energy resolution of an electron time-of-flight technique, and incorporated the PFI-PE technique with multi-bunch VUV synchrotron radiation.

• Research Organization: Lawrence Berkeley Lab., CA (United States)
• DOE Contract Number: AC03-76SF00098
• OSTI ID: 604271
• Report Number(s): LBNL--39981; ON: DE97007345
• Country of Publication: United States
• Language: English

Related Subjects

43 PARTICLE ACCELERATORS
66 PHYSICS
COMBUSTION PRODUCTS
IONIZATION
MOLECULES
PHOTOELECTRON SPECTROSCOPY
THRESHOLD ENERGY