skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: Vibrational branching ratios following two-color excitation of autoionizing np Rydberg states of H 2

Abstract

Two-color resonantly enhanced multiphoton ionization-photoelectron spectroscopy (REMPI-PES) was used to determine vibrational branching ratios following autoionization of the ungerade npσ 1Σ + u and npπ 1Π u Rydberg states of H 2. In this two-step experiment, one laser used to excite the two photon transition to the E,F 1Σ + g, v' = E2, J' = 1 state, and a second laser was used to access the autoionizing Rydberg states near the H + 2X 2Σ + g, v + = 2 ionization limit. Electrons corresponding to the formation of H + 2X 2Σ + g, v + = 0 and 1 were collected and energy analyzed using a magnetic bottle electron spectrometer. In agreement with the well-known propensity rule for vibrational autoionization, the vibrational branching ratios strongly favor the final ionic state that corresponds to the minimum change in vibrational quantum number. In general, the branching ratio into the v + = 1 channel is 94%--96%, while that into the v + = 0 channel is 4%--6%; however, two major deviations from this trend were observed for Rydberg states that are perturbed by the 3pπ 1Π u, v = 9 and 4pσ 1Σ + u, v = 7 states.more » Although these low n/high v interlopers were not observed in the present work (since their ionization efficiency is near zero), interchannel coupling apparently causes their influence to be felt by nearby Rydberg states, resulting in v +=0 branching ratios as high as 18%. A number of additional studies suggested by these initial results are discussed.« less

Authors:
 [1];  [1];  [1];  [1];  [1]
  1. Argonne National Laboratory (ANL), Argonne, IL (United States)
Publication Date:
Research Org.:
Argonne National Lab. (ANL), Argonne, IL (United States)
Sponsoring Org.:
US Department of Energy, Office of Health and Environment Research
OSTI Identifier:
7128598
DOE Contract Number:  
W-31-109-ENG-38
Resource Type:
Journal Article
Journal Name:
Journal of Chemical Physics
Additional Journal Information:
Journal Volume: 89; Journal Issue: 1; Journal ID: ISSN 0021-9606: JCPSA6
Publisher:
American Institute of Physics (AIP)
Country of Publication:
United States
Language:
English
Subject:
74 ATOMIC AND MOLECULAR PHYSICS; HYDROGEN; MULTI-PHOTON PROCESSES; PHOTOELECTRON SPECTROSCOPY; PHOTOIONIZATION; RYDBERG STATES; AUTOIONIZATION; BRANCHING RATIO; ELECTRON SPECTROSCOPY; ELEMENTS; ENERGY LEVELS; EXCITED STATES; IONIZATION; NONMETALS; SPECTROSCOPY; 640302* - Atomic, Molecular & Chemical Physics- Atomic & Molecular Properties & Theory

Citation Formats

O’Halloran, M. A., Dehmer, Patricia M., Tomkins, F. S., Pratt, Stephen T., and Dehmer, Joseph L. Vibrational branching ratios following two-color excitation of autoionizing np Rydberg states of H2. United States: N. p., 1988. Web. doi:10.1063/1.455463.
O’Halloran, M. A., Dehmer, Patricia M., Tomkins, F. S., Pratt, Stephen T., & Dehmer, Joseph L. Vibrational branching ratios following two-color excitation of autoionizing np Rydberg states of H2. United States. doi:10.1063/1.455463.
O’Halloran, M. A., Dehmer, Patricia M., Tomkins, F. S., Pratt, Stephen T., and Dehmer, Joseph L. Fri . "Vibrational branching ratios following two-color excitation of autoionizing np Rydberg states of H2". United States. doi:10.1063/1.455463.
@article{osti_7128598,
title = {Vibrational branching ratios following two-color excitation of autoionizing np Rydberg states of H2},
author = {O’Halloran, M. A. and Dehmer, Patricia M. and Tomkins, F. S. and Pratt, Stephen T. and Dehmer, Joseph L.},
abstractNote = {Two-color resonantly enhanced multiphoton ionization-photoelectron spectroscopy (REMPI-PES) was used to determine vibrational branching ratios following autoionization of the ungerade npσ 1Σ+u and npπ 1Πu Rydberg states of H2. In this two-step experiment, one laser used to excite the two photon transition to the E,F 1Σ+g, v' = E2, J' = 1 state, and a second laser was used to access the autoionizing Rydberg states near the H+2X 2Σ+g, v+ = 2 ionization limit. Electrons corresponding to the formation of H+2X 2Σ+g, v+ = 0 and 1 were collected and energy analyzed using a magnetic bottle electron spectrometer. In agreement with the well-known propensity rule for vibrational autoionization, the vibrational branching ratios strongly favor the final ionic state that corresponds to the minimum change in vibrational quantum number. In general, the branching ratio into the v+ = 1 channel is 94%--96%, while that into the v+ = 0 channel is 4%--6%; however, two major deviations from this trend were observed for Rydberg states that are perturbed by the 3pπ 1Πu, v = 9 and 4pσ 1Σ+u, v = 7 states. Although these low n/high v interlopers were not observed in the present work (since their ionization efficiency is near zero), interchannel coupling apparently causes their influence to be felt by nearby Rydberg states, resulting in v+=0 branching ratios as high as 18%. A number of additional studies suggested by these initial results are discussed.},
doi = {10.1063/1.455463},
journal = {Journal of Chemical Physics},
issn = {0021-9606: JCPSA6},
number = 1,
volume = 89,
place = {United States},
year = {1988},
month = {1}
}