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  • 1
    Electronic Resource
    Electronic Resource
    Collision dynamics of OH(X 2Πi,v=12) (1990)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 93 (1990), S. 5741-5746 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Collisional removal rate constants for the OH radical in v=12 of the ground electronic state are measured for the colliders CO2, O2, N2, H2, He, and Ar. OH molecules, generated in v=8 by the reaction of hydrogen atoms with ozone, are excited to v=12 by direct overtone excitation with pulsed infrared laser light. The temporal evolution of the v=12 radicals is probed as a function of collider gas pressure by a time-delayed pulsed ultraviolet probe laser. The probe laser is used to excite the molecules via the B 2Σ+–X 2Πi(0,12) electronic transition, and the resulting B 2Σ+–A 2Σ+ fluorescence is detected. We measure rate constants for CO2:(5.6±1.5)×10−11; O2:(1.6±0.2)×10−11; He:(3.6±0.6)×10−12; H2:(3.0±0.8)×10−12; Ar:(2.6±0.5)×10−12; N2:(2.5±0.7)×10−12 (all in units of cm3 s−1). These rate constants are over fifty times faster in all cases than the vibrational relaxation rate constants for the lower levels (v=1 and v=2) of the ground state.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.459567
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  • 2
    Electronic Resource
    Electronic Resource
    Electronic quenching, fluorescence lifetime, and spectroscopy of the A 3Πu state of NCN (1989)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 91 (1989), S. 1987-1993 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Laser-induced fluorescence of the NCN radical was observed downstream of a microwave discharge of N2 and CF4 in He via the A 3Πu–X 3Σ−g transition near 329 nm. The zero-pressure fluorescence lifetime of the 000 vibrational level of the A state was measured from the time-resolved laser-induced fluorescence to be 183±6 ns. Other spectral features were observed both to the blue and red of the 000–000 band. The blue-shifted features are tentatively assigned to the 020–000, 100–000, 030–010, and 110–010 vibrational bands. Quenching cross sections were determined for NCN (A 3Πu, 000) at 300 K for Ar, Kr, Xe, O2, CO, CO2, N2O, SF6, NO, and NO2. The molecules He, N2, and CF4 are inefficient quenchers and upper limits only were obtained. The large variation in cross section among the colliders does not correlate with predictions of simple electronic quenching models.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.457057
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  • 3
    Electronic Resource
    Electronic Resource
    Vibrationally excited O2 in flames: Measurements on v‘=9–11 by laser-induced fluorescence (1987)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 86 (1987), S. 2500-2504 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Vibrationally-excited ground state O2 is detected in a CH4/O2 flame in levels v‘=9–11 by laser-induced fluorescence in the B 3Σ−u–X 3Σ−g Schumann–Runge system. Accurate line positions are measured by calibration against OH(A–X) lines appearing in the same spectra. Signal levels indicate that measurements up to at least v‘=18 should be practical in such flames. The absolute energies of the three vibrational levels agree very well with RKR calculations of Albritton, based on earlier experimental work, but there is substantial disagreement for v‘=11 with the extensive data of Creek and Nicholls.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.452101
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  • 4
    Electronic Resource
    Electronic Resource
    Quenching of OH(A 2Σ+, v'=0) by NH3 from 250 to 1400 K (1986)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 85 (1986), S. 1898-1903 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The rate constant for collisional removal of the v′=0 level of the A 2Σ+ excited state of the OH radical by NH3 is measured over the temperature range 250–1400 K. The thermally averaged cross section σQ near room temperature is roughly twice its value at 900 K of ∼40 A(ring)2. Between 850 and 1400 K, no variation of σQ with temperature is observed. This temperature dependence is consistent with a quenching mechanism dominated by long range attractive forces.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.451133
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  • 5
    Electronic Resource
    Electronic Resource
    Intramultiplet energy transfer in the collisions of 3p 4D0 nitrogen atoms with nitrogen molecules (1989)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 91 (1989), S. 2200-2205 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Two-photon excitation at 211 nm combined with wavelength-resolved detection near 870 nm is used to study intramultiplet energy transfer in the 2s22p23p 4D0 state of nitrogen atoms resulting from collisions with nitrogen molecules. The thermally averaged cross sections at 300 K vary from 36±10 A(ring)2 for 4D01/2→4D03/2 to 3±3 A(ring)2 for 4D07/2→4D01/2. The cross sections for ΔJ=1 are larger than for ΔJ=2 which in turn are larger than for ΔJ=3. When 3p4D07/2 is excited with linearly polarized light, the fluorescence polarization is nonzero and independent of N2 pressure. Thus, the cross section for transfer between magnetic sublevels is smaller than those for transfer out of that fine-structure level.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.457029
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  • 6
    Electronic Resource
    Electronic Resource
    Radiative lifetime and quenching of the 3p 4D0 state of atomic nitrogen (1987)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 86 (1987), S. 4876-4884 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The radiative lifetime of nitrogen atoms in the 3p 4D0 state is determined to be 43±3 ns, and the total removal rate constants from the excited 3p 4D0 state of nitrogen atoms are measured for collisions with He, Ne, Ar, Kr, Xe, and N2. In a low pressure discharge flow reactor, the 3p 4D0 state is prepared by two-photon excitation from the 4S0 ground state of atomic nitrogen. Time-resolved fluorescence from the 3p 4D0→3s 4P transition monitors the temporal evolution of the population in the 3p 4D0 state. As the rare gases become heavier with a more complex electron cloud, the quenching rate constants increase from less than 0.6×10−11 cm3 s−1 for He to a value of 66±12×10−11 cm3 s−1 for Xe. Collision mechanisms which might account for such a dramatic increase are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.452658
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  • 7
    Electronic Resource
    Electronic Resource
    Erratum: Laser-induced fluorescence of the B 2Σ+–X 2Πi system of OH: Detection of v‘=8 and 9 [J. Chem. Phys. 90, 3484 (1989)] (1990)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 92 (1990), S. 818-818 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.458631
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  • 8
    Electronic Resource
    Electronic Resource
    Laser-induced fluorescence of the B 2Σ+–X 2Πi system of OH: Detection of v''=8 and 9 (1989)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 90 (1989), S. 3484-3489 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The previously unobserved B 2Σ+–X 2Πi electronic system of OH is detected by laser-induced fluorescence in a low-pressure flow system. OH is produced in high vibrational levels of the ground electronic state by the H+O3 reaction. Light from a frequency-doubled tunable dye laser excites the radical via the (0,8), (0,9), and (1,8) bands of the B 2Σ+–X 2Πi transistion at 225, 236, and 221 nm, respectively. The fluorescence is detected in the B 2Σ+–A 2Σ+ system in the visible and near ultraviolet. Measured emission intensities in the (0,3) to (0,9) and the (1,3) to (1,9) bands of B–A are in good agreement with previous theoretical calculations. The experimental branching ratio for emission between the B–A (0,3) and B–X (0,10) bands is about three times larger than theoretically predicted. Detection of high-lying vibrational levels in the electronic ground state, v''=6 through 15, for experiments in collision dynamics and reaction kinetics, is feasible using the B–X system.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.455858
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  • 9
    Electronic Resource
    Electronic Resource
    Collisional removal of O2(b 1Σg+,υ=2,3) (2002)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 116 (2002), S. 4877-4885 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The temperature dependence of the collisional removal of O2 in the υ=3 level of the b 1Σg+ state by N2, O2, and CO2 was investigated at room temperature and below. Measurements on the υ=2 level with the colliders, O2, N2O, Ar, and He are also reported. For υ=3 removal by O2, the trend of sharply decreasing loss rate coefficients with increasing υ is seen to continue. For example, at 200 K the rate coefficient for collisional removal of O2 from the υ=3 level by O2 is some three orders of magnitude smaller than that for the υ=1 level. We argue that the mechanism of the deactivation is electronic–electronic (E–E) energy transfer. Observation of emission from a broad range of O2(b 1Σg+) vibrational levels in the terrestrial nightglow, recently discovered in astronomical sky spectra, show less than an order of magnitude difference in population between the more highly populated υ=3 level and the less populated υ=1 level. The implications of these two observations on the vibrational-level-specific atmospheric sources of vibrationally excited molecules in the b 1Σg+ electronic state are explored. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1456026
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  • 10
    Electronic Resource
    Electronic Resource
    Laser double-resonance study of the collisional removal of O2 (A 3Σ+u, ν=6, 7, and 9) with O2, N2, CO2, Ar, and He (1994)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 101 (1994), S. 7415-7422 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The collisional removal of O2 molecules prepared in selected vibrational levels of the A 3Σ+u state is studied using a two-laser double-resonance technique. The output of the first laser excites the O2 to A 3Σ+u, ν=6, 7, or 9, and the ultraviolet output of the second laser monitors these levels via resonance-enhanced ionization through either the ν=5 level of the C 3Πg Rydberg state, or the valence state or states tentatively associated with the 5 3Πg state. The temporal evolution of the A 3Σ+u state vibrational level is observed by scanning the time delay between the two pulsed lasers. Collisional removal rate constants are obtained for A 3Σ+u, ν=7 and 9 colliding with O2, N2, CO2, Ar, and He; and for ν=6 colliding with O2 and N2. We find the collisional removal of the A 3Σ+u state to be fast (k≥10−11 cm3 s−1) for all colliders studied. The rate constants vary by about an order of magnitude from the fastest collisional deactivator, CO2 to the slowest studied, the rare gases Ar and He. The rate constants for the atmospherically important colliders O2 and N2 are similar in magnitude and suggest that N2 collisions will dominate the removal rate in the Earth's atmosphere.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.468418
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