Reaction and reorientation of electronically excited H₂(B)

Thesis/Dissertation · Tue Sep 01 04:00:00 EDT 1992

DOI:https://doi.org/10.2172/10140848· OSTI ID:10140848

Pibel, Charles David ^[1]

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1. Univ. of California, Berkeley, CA (United States)

The room temperature rate (TR) constants for fluorescence quenching fluorescence of H₂, HD, and D₂ B ¹Σ$$+\atop{u}$$ by ⁴He were measured as a function of the initially excited rotational and vibrational level of the hydrogen molecule, and the RT rate constants for molecular angular momentum reorientation of H₂, HD and D₂ (B ¹Σ$$+\atop{u}$$. v'=0, J'=1, M_J=0) in collisions with He, Ne, Ar and H₂(X ¹Σ$$+\atop{g}$$ ) were also measured. Vibrational state dependence of the quenching cross sections fits a vibrationally adiabatic model of the quenching process. From the vibrational state dependence of the quenching cross section, the barrier height for the quenching reaction is found to be 250±40 cm^-1, and the difference in the H-H stretching frequencies between H₂(B) and the H₂-He complex at the barrier to reaction is 140±80 cm^-1. The effective cross sections for angular momentum reorientation in collisions of H₂, HD, D₂ with He and Ne were found to be about 30 Ų and were nearly the same for each isotope and with He and Ne as collision partners. Cross sections forreorientation of HD and D₂ in collisions with Ar were 10.6±2.0 and 13.9±3.0 Ų, respectively. Reorientation of D₂(B) in collisions with room temperature H₂(X) occurs with a 7.6±3.4 Ų cross section. Calculated cross sections using semiclassical and quantum close coupled methods give cross sections for reorientation of H₂(B) and D₂(B) in collisions with He that agree quantitatively with experiment. Discrepancy between the calculated and experimental cross sections for HD(B)-HE are likely due to rotational relaxation in HD a Turbo PASCAL version of the data-taking program is included.

• Research Organization: Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
• Sponsoring Organization: USDOE
• DOE Contract Number: AC03-76SF00098
• OSTI ID: 10140848
• Report Number(s): LBL--33473; ON: DE93010435
• Country of Publication: United States
• Language: English

Related Subjects

664300
664400
74 ATOMIC AND MOLECULAR PHYSICS
ANGULAR MOMENTUM TRANSFER
ATOM-MOLECULE COLLISIONS
COLLISION PHENOMENA
COMPUTER PROGRAM DOCUMENTATION
CROSS SECTIONS
DEUTERIUM
EXPERIMENTALLY DERIVED INFORMATION ON ATOMIC AND MOLECULAR PROPERTIES
FLUORESCENCE
HELIUM
HELIUM 4
HYDROGEN
HYDROGEN DEUTERIDE
NEON
ORIENTATION
SCINTILLATION QUENCHING
VIBRATIONAL STATES