The fluorescence action spectra of some saturated hydrocarbon liquids for excitation energies above and below their ionization thresholds

Journal Article · Thu Apr 01 00:00:00 EST 1993 · Journal of Chemical Physics; (United States)

DOI:https://doi.org/10.1063/1.464890· OSTI ID:6688263

Ostafin, A E; Lipsky, S ^[1]

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1. Department of Chemistry, University of Minnesota, Minneapolis, Minnesota 55455 (United States)

Fluorescence action spectra have been obtained for the neat liquids, [ital cis]-decalin, [ital trans]-decalin, bicyclohexyl, cyclohexane, methylcyclohexane, isobutylcyclohexane, 2,3,4-trimethylpentane, 2,3-dimethylbutane, 3-methylhexane, 3-methylpentane, [ital n]-decane, [ital n]-dodecane, and [ital n]-pentadecane at excitation energies, [epsilon], ranging from their absorption onsets (at ca. 7 eV) to 10.3 eV. For all compounds, with the exception of [ital cis]-decalin, the fluorescence quantum yield is observed to monotonically decline with increasing [epsilon], reaching a minimum value at an energy, [epsilon][sub [ital m]] (a few tenths of an eV above the liquid phase ionization threshold, [epsilon][sub [ital l]]) followed by a slow increase. In the case of [ital cis]-decalin, the fluorescence quantum yield remains constant over the entire range of excitation energies studied, permitting its use as a quantum counter replacing the standard sodium salicylate, at least over a spectral range from 185 to 120 nm. The recovery of the fluorescence quantum yield for [epsilon][gt][epsilon][sub [ital m]] is attributed to an increasing probability for electron ejection followed by [ital e][sup [minus]]+RH[sup +] geminate recombination, to produce an excited state of RH with energy less than [epsilon][sub [ital l]]. From a simple analysis of the action spectrum, a lower bound estimate of the electron ejection probability, [phi][sub [plus minus]], is obtained as a function of [epsilon]. In the case of cyclohexane, where [phi][sub [plus minus]] has been obtained by other techniques at [epsilon][congruent]10 eV, the lower bound estimate agrees with the experimental value. From this agreement, arguments are presented to make plausible the conjecture that in all these liquids, the initially produced [ital e][sup [minus]]+RH[sup +] geminate ion pair first rapidly internally converts to an ion-pair state ca.

• OSTI ID: 6688263
• Journal Information: Journal of Chemical Physics; (United States), Vol. 98:7; ISSN 0021-9606
• Country of Publication: United States
• Language: English

Related Subjects

74 ATOMIC AND MOLECULAR PHYSICS
BUTANE
FLUORESCENCE
CYCLOHEXANE
DECALIN
DECANE
DODECANE
HEXANE
HEXYL RADICALS
ISOBUTYL RADICALS
METHYL RADICALS
PENTANE
ENERGY DEPENDENCE
EXCITATION
HYDROCARBONS
IONIZATION POTENTIAL
LIQUIDS
SATURATION
THRESHOLD ENERGY
ALKANES
ALKYL RADICALS
CYCLOALKANES
ENERGY
ENERGY-LEVEL TRANSITIONS
FLUIDS
LUMINESCENCE
ORGANIC COMPOUNDS
RADICALS
664200* - Spectra of Atoms & Molecules & their Interactions with Photons- (1992-)