Interrogating the vibrational relaxation of highly excited polyatomics with time-resolved diode laser spectroscopy: C sub 6 H sub 6 , C sub 6 D sub 6 , and C sub 6 F sub 6 +CO sub 2

Journal Article · Wed May 15 04:00:00 EDT 1991 · Journal of Chemical Physics; (USA)

DOI:https://doi.org/10.1063/1.460277· OSTI ID:5539773

Sedlacek, A J; Weston, Jr, R E ^[1]; Flynn, G W ^[2]

---

1. Brookhaven National Laboratory, Department of Chemistry, Upton, New York 11973 (USA)
2. Department of Chemistry and Columbia Radiation Laboratory, Columbia University, New York, New York 10027 (USA)

The vibrational relaxation of highly excited ground state benzene, benzene {ital d}{sub 6}, and hexafluorobenzene by CO{sub 2} has been investigated with high resolution diode laser spectroscopy. The vibrationally hot polyatomics are formed by single photon 248 nm excitation to the S{sub 1} state followed by rapid radiationless transitions. It has been found that in all cases less than 1% of the energy initially present in the polyatomics is deposited into the high frequency mode of CO{sub 2} ({nu}{sub 3}). An investigation of the CO{sub 2}(00{sup 0}1) nascent rotational distribution under single collision conditions reveals that very little rotational excitation accompanies vibrational energy transfer to the {nu}{sub 3} mode. The CO{sub 2}({nu}{sub 3}) rotational states can be described by temperatures, {ital T}{sub rot}, as follows: C{sub 6}H{sub 6}, {ital T}{sub rot} =360{plus minus}30 K; C{sub 6}D{sub 6}, {ital T}{sub rot} =350{plus minus}35 K and C{sub 6}F{sub 6}, {ital T}{sub rot} =340{plus minus}23 K. An estimate of {l angle}{Delta}{ital E}{r angle}{sub {nu}3}, the mean energy transferred to the CO{sub 2} {nu}{sub 3} mode per collision, suggests that as the availability of low frequency modes in the excited molecule increases, less energy is deposited into the high frequency mode of CO{sub 2}. Finally, evidence is presented suggesting that even at moderate laser fluences, the two-photon ionization of benzene can lead to substantial CO{sub 2} {nu}{sub 3} excitation via electron+CO{sub 2} inelastic collisions.

• DOE Contract Number: AC02-76CH00016; FG02-88ER13937
• OSTI ID: 5539773
• Journal Information: Journal of Chemical Physics; (USA), Journal Name: Journal of Chemical Physics; (USA) Vol. 94:10; ISSN JCPSA; ISSN 0021-9606
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400102 -- Chemical & Spectral Procedures
640302* -- Atomic
Molecular & Chemical Physics-- Atomic & Molecular Properties & Theory
74 ATOMIC AND MOLECULAR PHYSICS
AROMATICS
BENZENE
CARBON COMPOUNDS
CARBON DIOXIDE
CARBON OXIDES
CHALCOGENIDES
CHEMISTRY
COLLISIONS
DEUTERIUM COMPOUNDS
ELECTROMAGNETIC RADIATION
ENERGY LEVELS
ENERGY TRANSFER
ENERGY-LEVEL TRANSITIONS
EXCITATION
EXCITED STATES
FLUORINATED AROMATIC HYDROCARBONS
HALOGENATED AROMATIC HYDROCARBONS
HYDROCARBONS
HYDROGEN COMPOUNDS
LASER SPECTROSCOPY
MOLECULE COLLISIONS
MOLECULE-MOLECULE COLLISIONS
MOLECULES
ORGANIC COMPOUNDS
ORGANIC FLUORINE COMPOUNDS
ORGANIC HALOGEN COMPOUNDS
OXIDES
OXYGEN COMPOUNDS
PHOTOCHEMISTRY
POLYATOMIC MOLECULES
RADIATIONS
RELAXATION
SPECTROSCOPY
ULTRAVIOLET RADIATION
VIBRATIONAL STATES