Infrared-ultraviolet double-resonance measurements on the temperature dependence of relaxation from specific rovibronic levels in NO(X2Π, v = 2, J) and (X2Π, v = 3, J)

Meez Islam, Ian W M Smith, Jörg Wiebrecht

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Abstract

Infrared-ultraviolet double-resonance experiments have been performed on NO at three temperatures, 295, 200, and 80 K, to measure rate constants for (a) total relaxation from selected levels in the v = 2, Ω = 1/2 and v = 3, Ω = 1/2 rotational manifolds of the X2Π electronic ground state with several collision partners (M = NO, He, Ar, H2, N2, CO, and CO2), and (b) vibrational self-relaxation from v = 2 and v = 3. NO molecules were initially prepared in selected rovibronic levels by tuning the output from an optical parametric oscillator to lines in the (2,0) or (3,0) infrared overtone bands. Loss of population from the initially excited level was observed by making time-resolved laser-induced fluorescence measurements on appropriate lines in the (2,2) and (2,3) bands of the A2Σ+-X2Π electronic system of NO. The thermally averaged cross sections for total rotational relaxation are found to be essentially independent of rotational state and temperature. The light collision partners (He, H2) are the least effective, with the molecular species (NO, N2, CO, and CO2) rather more effective than Ar. The results are compared with previous directly determined values for rotational relaxation in v = 2 and higher vibrational levels and with cross sections inferred from measurements of line-broadening. It is clear that vibrational self-relaxation of NO(v=2) and NO(v=3) occurs by vibration-vibration (V-V) exchange, NO(v) + NO(v=0) → NO(v-1 ) + NO(v=1), at a rate which is almost independent of temperature and which seems to be uninfluenced by the presence of spin-orbit degeneracy in, and specific attractive forces between, the NO collision partners.

Original languageEnglish
Pages (from-to)9285-9290
Number of pages6
JournalJournal of Physical Chemistry
Volume98
Issue number37
Publication statusPublished - 1 Dec 1994

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Carbon Monoxide
Infrared radiation
temperature dependence
Optical parametric oscillators
collisions
Temperature
Ground state
Rate constants
Orbits
Tuning
Fluorescence
vibration
cross sections
rotational states
parametric amplifiers
Molecules
electronics
Lasers
laser induced fluorescence
temperature

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@article{7f5aa5b95fae47c4813a9a44f727ce47,
title = "Infrared-ultraviolet double-resonance measurements on the temperature dependence of relaxation from specific rovibronic levels in NO(X2Π, v = 2, J) and (X2Π, v = 3, J)",
abstract = "Infrared-ultraviolet double-resonance experiments have been performed on NO at three temperatures, 295, 200, and 80 K, to measure rate constants for (a) total relaxation from selected levels in the v = 2, Ω = 1/2 and v = 3, Ω = 1/2 rotational manifolds of the X2Π electronic ground state with several collision partners (M = NO, He, Ar, H2, N2, CO, and CO2), and (b) vibrational self-relaxation from v = 2 and v = 3. NO molecules were initially prepared in selected rovibronic levels by tuning the output from an optical parametric oscillator to lines in the (2,0) or (3,0) infrared overtone bands. Loss of population from the initially excited level was observed by making time-resolved laser-induced fluorescence measurements on appropriate lines in the (2,2) and (2,3) bands of the A2Σ+-X2Π electronic system of NO. The thermally averaged cross sections for total rotational relaxation are found to be essentially independent of rotational state and temperature. The light collision partners (He, H2) are the least effective, with the molecular species (NO, N2, CO, and CO2) rather more effective than Ar. The results are compared with previous directly determined values for rotational relaxation in v = 2 and higher vibrational levels and with cross sections inferred from measurements of line-broadening. It is clear that vibrational self-relaxation of NO(v=2) and NO(v=3) occurs by vibration-vibration (V-V) exchange, NO(v) + NO(v=0) → NO(v-1 ) + NO(v=1), at a rate which is almost independent of temperature and which seems to be uninfluenced by the presence of spin-orbit degeneracy in, and specific attractive forces between, the NO collision partners.",
author = "Meez Islam and Smith, {Ian W M} and J{\"o}rg Wiebrecht",
year = "1994",
month = "12",
day = "1",
language = "English",
volume = "98",
pages = "9285--9290",
journal = "Journal of Physical Chemistry",
issn = "0022-3654",
publisher = "American Chemical Society",
number = "37",

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Infrared-ultraviolet double-resonance measurements on the temperature dependence of relaxation from specific rovibronic levels in NO(X2Π, v = 2, J) and (X2Π, v = 3, J). / Islam, Meez; Smith, Ian W M; Wiebrecht, Jörg .

In: Journal of Physical Chemistry, Vol. 98, No. 37, 01.12.1994, p. 9285-9290.

Research output: Contribution to journalArticleResearchpeer-review

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N2 - Infrared-ultraviolet double-resonance experiments have been performed on NO at three temperatures, 295, 200, and 80 K, to measure rate constants for (a) total relaxation from selected levels in the v = 2, Ω = 1/2 and v = 3, Ω = 1/2 rotational manifolds of the X2Π electronic ground state with several collision partners (M = NO, He, Ar, H2, N2, CO, and CO2), and (b) vibrational self-relaxation from v = 2 and v = 3. NO molecules were initially prepared in selected rovibronic levels by tuning the output from an optical parametric oscillator to lines in the (2,0) or (3,0) infrared overtone bands. Loss of population from the initially excited level was observed by making time-resolved laser-induced fluorescence measurements on appropriate lines in the (2,2) and (2,3) bands of the A2Σ+-X2Π electronic system of NO. The thermally averaged cross sections for total rotational relaxation are found to be essentially independent of rotational state and temperature. The light collision partners (He, H2) are the least effective, with the molecular species (NO, N2, CO, and CO2) rather more effective than Ar. The results are compared with previous directly determined values for rotational relaxation in v = 2 and higher vibrational levels and with cross sections inferred from measurements of line-broadening. It is clear that vibrational self-relaxation of NO(v=2) and NO(v=3) occurs by vibration-vibration (V-V) exchange, NO(v) + NO(v=0) → NO(v-1 ) + NO(v=1), at a rate which is almost independent of temperature and which seems to be uninfluenced by the presence of spin-orbit degeneracy in, and specific attractive forces between, the NO collision partners.

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