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Title: Rotational state distributions from vibrational autoionization of H₂

Abstract

Optical--optical double-resonance excitation together with electron spectroscopy was used to measure the H⁺₂ rotational state distributions produced by vibrational autoionization of singlet n p Rydberg states of H₂ . In the two-color excitation scheme, one laser was used to excite the two-photon transition to the H₂ E, F ¹Σ⁺ g, v'=1, J'=1 state, and a second laser was used to probe single-photon transitions to the vibrationally autoionized n p Rydberg series converging to the X ²Σ⁺ g, v⁺=1, N¯⁺=1 and N¯⁺= 3 levels of the ion. The expected P(1)n pσ, Q(1)n pπ, R(1)n p1, and R(1)n p3 Rydberg series converging to v⁺=1 were observed and assigned, as were several interlopers converging to higher vibrational levels of the ion. Rotationally resolved photoelectron spectra were determined for all of the autoionizing transitions by using a magnetic bottle electron spectrometer. Under the normal assumptions that p waves are ejected and that spin effects are negligible, vibrational autoionization of the upper levels of the P(1)n pσ and Q(1)n pπ transitions should produce only v⁺=0, N⁻⁺=1, while vibrational autoionization of the upper levels of the R(1)np1 and R(1)n p3 transitions should produce a mixture of v⁺=0, N¯⁺= 1 and v⁺=0, N¯⁺=3. Significant deviations from thesemore » expectations were observed. For example, vibrational autoionization of the upper levels of the Q(1)n pπ transitions produced substantial amounts of v⁺=0, N¯⁺=3, while vibrational autoionization of the upper levels of certain Q(1)n pπ, R(1)n p1, and interloper transitions produced nonnegligible amounts of v⁺=0, N¯⁺=5. This indicates that vibrational autoionization of n pπ Rydberg states is accompanied by rotational state changes in the H⁺₂ core to an unexpected degree, and that additional mechanisms for exchange of angular momentum within the excited complex must be considered. Possible contributing mechanisms are critically assessed.« less

Authors:
 [1];  [1];  [1];  [1];  [2]
  1. Argonne National Lab. (ANL), Argonne, IL (United States)
  2. Univ. of Oklahoma, Norman, OK (United States)
Publication Date:
Research Org.:
Argonne National Lab. (ANL), Argonne, IL (United States)
Sponsoring Org.:
USDOE; Office of Health and Environmental Research (OHER)
OSTI Identifier:
6068335
DOE Contract Number:  
W-31-109-ENG-38
Resource Type:
Journal Article
Journal Name:
Journal of Chemical Physics
Additional Journal Information:
Journal Volume: 90; Journal Issue: 11; Journal ID: ISSN 0021-9606
Publisher:
American Institute of Physics (AIP)
Country of Publication:
United States
Language:
English
Subject:
74 ATOMIC AND MOLECULAR PHYSICS; HYDROGEN; AUTOIONIZATION; ENERGY-LEVEL DENSITY; DISTRIBUTION; ELECTRON SPECTROSCOPY; ENERGY TRANSFER; LASER RADIATION; MULTI-PHOTON PROCESSES; ROTATIONAL STATES; RYDBERG STATES; VIBRATIONAL STATES; ELECTROMAGNETIC RADIATION; ELEMENTS; ENERGY LEVELS; EXCITED STATES; IONIZATION; NONMETALS; RADIATIONS; SPECTROSCOPY; 640302* - Atomic, Molecular & Chemical Physics- Atomic & Molecular Properties & Theory

Citation Formats

Dehmer, Joseph L., Dehmer, Patricia M., Pratt, Stephen T., Tomkins, F. S., and O’Halloran, M. A. Rotational state distributions from vibrational autoionization of H₂. United States: N. p., 1989. Web. doi:10.1063/1.456341.
Dehmer, Joseph L., Dehmer, Patricia M., Pratt, Stephen T., Tomkins, F. S., & O’Halloran, M. A. Rotational state distributions from vibrational autoionization of H₂. United States. doi:10.1063/1.456341.
Dehmer, Joseph L., Dehmer, Patricia M., Pratt, Stephen T., Tomkins, F. S., and O’Halloran, M. A. Sun . "Rotational state distributions from vibrational autoionization of H₂". United States. doi:10.1063/1.456341.
@article{osti_6068335,
title = {Rotational state distributions from vibrational autoionization of H₂},
author = {Dehmer, Joseph L. and Dehmer, Patricia M. and Pratt, Stephen T. and Tomkins, F. S. and O’Halloran, M. A.},
abstractNote = {Optical--optical double-resonance excitation together with electron spectroscopy was used to measure the H⁺₂ rotational state distributions produced by vibrational autoionization of singlet n p Rydberg states of H₂ . In the two-color excitation scheme, one laser was used to excite the two-photon transition to the H₂ E, F ¹Σ⁺g, v'=1, J'=1 state, and a second laser was used to probe single-photon transitions to the vibrationally autoionized n p Rydberg series converging to the X ²Σ⁺g, v⁺=1, N¯⁺=1 and N¯⁺= 3 levels of the ion. The expected P(1)n pσ, Q(1)n pπ, R(1)n p1, and R(1)n p3 Rydberg series converging to v⁺=1 were observed and assigned, as were several interlopers converging to higher vibrational levels of the ion. Rotationally resolved photoelectron spectra were determined for all of the autoionizing transitions by using a magnetic bottle electron spectrometer. Under the normal assumptions that p waves are ejected and that spin effects are negligible, vibrational autoionization of the upper levels of the P(1)n pσ and Q(1)n pπ transitions should produce only v⁺=0, N⁻⁺=1, while vibrational autoionization of the upper levels of the R(1)np1 and R(1)n p3 transitions should produce a mixture of v⁺=0, N¯⁺= 1 and v⁺=0, N¯⁺=3. Significant deviations from these expectations were observed. For example, vibrational autoionization of the upper levels of the Q(1)n pπ transitions produced substantial amounts of v⁺=0, N¯⁺=3, while vibrational autoionization of the upper levels of certain Q(1)n pπ, R(1)n p1, and interloper transitions produced nonnegligible amounts of v⁺=0, N¯⁺=5. This indicates that vibrational autoionization of n pπ Rydberg states is accompanied by rotational state changes in the H⁺₂ core to an unexpected degree, and that additional mechanisms for exchange of angular momentum within the excited complex must be considered. Possible contributing mechanisms are critically assessed.},
doi = {10.1063/1.456341},
journal = {Journal of Chemical Physics},
issn = {0021-9606},
number = 11,
volume = 90,
place = {United States},
year = {1989},
month = {1}
}