Laboratory measurements and theoretical calculations of O{sub 2} A band electric quadrupole transitions
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California 91125 (United States)
- Process Measurements Division, National Institute of Standards and Technology, 100 Bureau Drive, Gaithersburg, Maryland 20899 (United States)
- Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, California 91109 (United States)
Frequency-stabilized cavity ring-down spectroscopy was utilized to measure electric quadrupole transitions within the {sup 16}O{sub 2} A band, b {sup 1}{sigma}{sub g}{sup +}(leftarrow)X {sup 3}{sigma}{sub g}{sup -}(0,0). We report quantitative measurements (relative uncertainties in intensity measurements from 4.4% to 11%) of nine ultraweak transitions in the {sup N}O, {sup P}O, {sup R}S, and {sup T}S branches with line intensities ranging from 3x10{sup -30} to 2x10{sup -29} cm molec.{sup -1}. A thorough discussion of relevant noise sources and uncertainties in this experiment and other cw-cavity ring-down spectrometers is given. For short-term averaging (t<100 s), we estimate a noise-equivalent absorption of 2.5x10{sup -10} cm{sup -1} Hz{sup -1/2}. The detection limit was reduced further by co-adding up to 100 spectra to yield a minimum detectable absorption coefficient equal to 1.8x10{sup -11} cm{sup -1}, corresponding to a line intensity of {approx}2.5x10{sup -31} cm molec.{sup -1}. We discuss calculations of electric quadrupole line positions based on a simultaneous fit of the ground and upper electronic state energies which have uncertainties <3 MHz, and we present calculations of electric quadrupole matrix elements and line intensities. The electric quadrupole line intensity calculations and measurements agreed on average to 5%, which is comparable to our average experimental uncertainty. The calculated electric quadrupole band intensity was 1.8(1)x10{sup -27} cm molec.{sup -1} which is equal to only {approx}8x10{sup -6} of the magnetic dipole band intensity.
- OSTI ID:
- 21316399
- Journal Information:
- Physical Review. A, Vol. 80, Issue 4; Other Information: DOI: 10.1103/PhysRevA.80.042513; (c) 2009 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA); ISSN 1050-2947
- Country of Publication:
- United States
- Language:
- English
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