Vacuum-ultraviolet stimulated emission from two-photon-excited molecular hydrogen
Intense vacuum-ultraviolet stimulated emission in molecular hydrogen, on both the Lyman and Werner bands, following excitation by two-quantum absorption at 193 nm on the X /sup 1/..sigma../sub g//sup +/..-->..E,F /sup 1/..sigma../sub g//sup +/ transition, has been observed. The shortest wavelength seen in the stimulated-emission spectrum was 117.6 nm corresponding to the C /sup 1/Pi/sub u/..-->..X /sup 1/..sigma../sub g//sup +/ (2-5) Q(2) transition. The C /sup 1/Pi/sub u/ state appears to be populated with a mechanism involving electron collisions. The radiative cascade mechanism found to lead to the vacuum-ultraviolet emissions on the Lyman band also causes strong infrared stimulated emission to occur on the E,F /sup 1/..sigma../sub g//sup +/..-->..B /sup 1/..sigma../sub u//sup +/ band. Two entirely separate radiative excitation channels are observed to play important roles in the state-selective molecular population of the E, F /sup 1/..sigma../sub g//sup +/ level. One involves two 193-nm quanta in the Xreverse arrowE,F amplitude while the other process combines a 193-nm quantum with a first Stokes-shifted photon in H/sub 2/. The optical Stark effect was seen to play a significant role in the excitation process with shifts of molecular resonances as large as approx.45 cm/sup -1/. Substantial deviations from Born-Oppenheimer behavior, resulting in a dramatic shift of the stimulated spectrum depending upon the excited-state rotational quantum number, were clearly observed for molecular levels close to the potential maximum separating the inner and outer wells of the E,F /sup 1/..sigma../sub g//sup +/ state. The maximum energy observed in the strongest stimulated line was approx.100 ..mu..J, a value corresponding to an energy conversion efficiency of approx.0.5%. The pulse duration of the stimulated emission is estimated from collisional data to be approx.10 ps, a figure indicating a maximum converted vacuum-ultraviolet power of approx.10 MW.
- Research Organization:
- Department of Physics, University of Illinois at Chicago, P. O. Box 4348, Chicago, Illinois 60680
- OSTI ID:
- 5676205
- Journal Information:
- Phys. Rev. A; (United States), Journal Name: Phys. Rev. A; (United States) Vol. 28:2; ISSN PLRAA
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
Molecular & Chemical Physics-- Atomic & Molecular Properties & Theory
74 ATOMIC AND MOLECULAR PHYSICS
COLLISIONS
CONVERSION
EFFICIENCY
ELECTROMAGNETIC RADIATION
ELEMENTS
EMISSION
ENERGY CONVERSION
ENERGY-LEVEL TRANSITIONS
EXCITATION
EXTREME ULTRAVIOLET RADIATION
FAR ULTRAVIOLET RADIATION
HYDROGEN
LASER RADIATION
LYMAN LINES
MOLECULE COLLISIONS
MULTI-PHOTON PROCESSES
NONMETALS
PHOTON COLLISIONS
PHOTON-MOLECULE COLLISIONS
QUANTUM EFFICIENCY
RADIATIONS
RAMAN SPECTRA
RESONANCE
SPECTRA
STIMULATED EMISSION
ULTRAVIOLET RADIATION