The CH2 b~1B1 - a~1 A1 Band Origin at 1.20 um

Journal Article · Thu Sep 01 04:00:00 EDT 2011 · Journal of Physical Chemistry A

OSTI ID:1040517

Sears, T J; Chang, C -H; Xin, J; Latsha, T; Otruba, E; Wang, Z; Hall, G E; Chang, B -C

The origin band in the {tilde b}{sup 1}B{sub 1}-{tilde a}{sup 1}A{sub 1} transition of CH{sub 2} near 1.2 {mu}m has been recorded at Doppler-limited resolution using diode laser transient absorption spectroscopy. The assignments of rotational transitions terminating in upper state levels with K{sub a} = 0 and 1, were confirmed by ground state combination differences and extensive optical-optical double resonance experiments. The assigned lines are embedded in a surprisingly dense spectral region, which includes a strong hot band, {tilde b}(0,1,0) K{sub a} = 0 - {tilde a}(0,1,0) K{sub a} = 1 sub-band lines, with combination or overtone transitions in the {tilde a}{sup 1}A{sub 1} state likely responsible for the majority of unassigned transitions in this region. From measured line intensities and an estimate of the concentration of CH{sub 2} in the sample, we find the transition moment square for the 000 {l_arrow} 110 transition in the {tilde b}{sup 1}B{sub 1}(0,0,0)0-{tilde a}{sup 1}A{sub 1}(0,0,0)1 sub-band is 0.005(1) D{sup 2}. Prominent {tilde b}{sup 1}B{sub 1}(0,1,0)0-{tilde a}{sup 1}A{sub 1}(0,1,0)1 hot band lines were observed in the same spectral region. Comparison of the intensities of corresponding rotational transitions in the two bands suggests the hot band has an intrinsic strength approximately 28 times larger than the origin band. Perturbations of the excited state K{sub a} = 0 and 1 levels are observed and discussed. The new measurements will lead to improved future theoretical modeling and calculations of the Renner-Teller effect between the {tilde a} and {tilde b} states in CH{sub 2}.

• Research Organization: BROOKHAVEN NATIONAL LABORATORY (BNL)
• Sponsoring Organization: USDOE SC OFFICE OF SCIENCE (SC)
• DOE Contract Number: AC02-98CH10886
• OSTI ID: 1040517
• Report Number(s): BNL--94613-2011-JA; KC0301020
• Journal Information: Journal of Physical Chemistry A, Journal Name: Journal of Physical Chemistry A Journal Issue: 34 Vol. 115
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
ABSORPTION SPECTROSCOPY
EXCITED STATES
GROUND STATES
LASERS
ORIGIN
RESOLUTION
RESONANCE
SIMULATION
TRANSIENTS