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The O(2p 3Pj) (j=2, 1, and 0) fragments produced in the 157 nm photodissociation of CO2 were detected by resonance-enhanced multiphoton ionization in a molecular beam. The Doppler profiles and fine-structure branching ratios were measured for the oxygen-atom photofragment in the 3Pj states. The Doppler profiles were analyzed to give an anisotropy parameter of β=2.0±0.2 and an internal energy equivalent to 3.9±0.3 vibrational quanta of CO. The fine-structure populations were found to be 0.70±0.05, 0.16±0.03, and 0.14±0.03 (with error bars of ±σ) for j=2, 1, and 0, respectively. A mechanism is proposed in which complex on the 1B2 surface undergoes intersystem crossing to the 3B2 surface. A phase-space model with a constraint on the impact parameter is shown to be consistent with the observed energy release. The nonstatistical fine-structure population could be caused by long-range interactions on the triplet surface. In a bulb experiment, O(3P) was produced by quenching of O(1D). The fine-structure populations of the resulting O(3Pj) were 0.64±0.04, 0.25±0.04, and 0.11±0.04. This state distribution is consistent with a long-lived complex which decays to give statistical products. [ABSTRACT FROM AUTHOR]

We have investigated the pressure dependence of the detection sensitivity of CO2, N2O and CH4 using wavelength modulation spectroscopy (WMS) with distributed feed-back diode lasers in the near infrared region. The spectral line shapes and the background noise of the second harmonics (2f) detection of the WMS were analyzed theoretically. We determined the optimum pressure conditions in the detection of CO2, N2O and CH4, by taking into consideration the background noise in the WMS. At the optimum total pressure for the detection of CO2, N2O and CH4, the limits of detection in the present system were determined. [ABSTRACT FROM AUTHOR]

Highlights: [•] We measured stable carbon isotope ratios of CO2 by a laser absorption spectrometer. [•] The H2O broadening coefficients of CO2 were determined. [•] The effect of humidity on δ13C determination was examined. [•] The spectrometer keeps constant measurement conditions over 12-h periods. [ABSTRACT FROM AUTHOR]