Observation of large vibration-to-vibration energy transfer collisions ([Delta][ital E][gt]3500 cm[sup [minus]1]) in quenching of highly excited NO[sub 2] by CO[sub 2] and N[sub 2]O

Journal Article · Tue Nov 15 04:00:00 EST 1994 · Journal of Chemical Physics; (United States)

DOI:https://doi.org/10.1063/1.468050· OSTI ID:6836711

Hartland, G V; Qin, D; Dai, H ^[1]

---

1. Department of Chemistry, University of Pennsylvania, Philadelphia, Pennsylvania 19104-6323 (United States)

Time-resolved Fourier transform infrared emission spectra, recorded after 475 nm excitation of NO[sub 2] in a CO[sub 2] or N[sub 2]O bath, show IR emission from collisionally populated vibrational levels of the bath gas. The frequency of the observed bands proves that the emission arises from either the (1,0[sup 0],1), (0,2[sup [ital l]],1), and/or (0,0[sup 0],2) levels of CO[sub 2] or N[sub 2]O. From the pressure dependence of the emission intensity it was determined that these levels are populated by single collisions with excited NO[sub 2]. Under typical conditions (1:10 ratio of NO[sub 2] to bath gas and 1--2 Torr total pressure) a steady state concentration is reached in our experiments where 0.016[plus minus]0.006 multiply excited CO[sub 2] molecules, or 0.03[plus minus]0.01 multiply excited N[sub 2]O molecules were generated per laser excited NO[sub 2]. A transition dipole coupling model is applied to explain these results, where the resonance conditions for vibration-to-vibration energy transfer are relaxed by extensive vibronic and vibrational couplings in highly excited NO[sub 2]. In this model the energy-dependent transition dipole of excited NO[sub 2] is derived from the time-resolved IR emission spectra. The probability of [Delta][ital v]=1 energy transfer collisions for excited NO[sub 2] with CO[sub 2] or N[sub 2]O can be accurately calculated. However, analysis of the time-resolved data shows that the probability for [Delta][ital v][gt]1 [ital V]--[ital V] energy transfer is ca. two orders of magnitude larger than the probability predicted by the dipole coupling model, and that NO[sub 2] molecules with energies as low as 5000 cm[sup [minus]1] have a non-negligible probability for exciting the overtone levels of CO[sub 2] and N[sub 2]O. Finally, it was found that the dipole coupling model also underestimates the probability for the [Delta][ital E][gt]10 000 cm[sup [minus]1] supercollisions deduced in previous experiments.

• DOE Contract Number: FG02-86ER13584
• OSTI ID: 6836711
• Journal Information: Journal of Chemical Physics; (United States), Journal Name: Journal of Chemical Physics; (United States) Vol. 101:10; ISSN JCPSA6; ISSN 0021-9606
• Country of Publication: United States
• Language: English

Related Subjects

664300* -- Atomic & Molecular Physics-- Collision Phenomena-- (1992-)
74 ATOMIC AND MOLECULAR PHYSICS
CARBON COMPOUNDS
CARBON DIOXIDE
CARBON OXIDES
CHALCOGENIDES
COLLISIONS
EMISSION SPECTRA
ENERGY LEVELS
ENERGY TRANSFER
EXCITED STATES
INFRARED SPECTRA
MOLECULE COLLISIONS
MOLECULE-MOLECULE COLLISIONS
NITROGEN COMPOUNDS
NITROGEN DIOXIDE
NITROGEN OXIDES
NITROUS OXIDE
OXIDES
OXYGEN COMPOUNDS
RELAXATION
RESOLUTION
SPECTRA
TIME RESOLUTION
TIMING PROPERTIES
VIBRATIONAL STATES