Optoacoustic detection of photodissociation and thermomolecular recombination in Cl/sub 2/

Journal Article · Sun Jul 15 04:00:00 EDT 1984 · J. Chem. Phys.; (United States)

OSTI ID:6035526

O'Connor, M T; Diebold, G J

In a spectrophone cell at pressures on the order of 1 atm, photodissociation of a homonuclear diatomic molecule gives two radicals which ultimately recombine in a three-body process to release an amount of heat equal to the energy of the incident photon. If the radiation producing the photodissociation is amplitude modulated, a periodic heating of the gas takes place that gives rise to a sound wave. Since the recombination process that liberates heat is bimolecular in the radical concentration, the equations describing the optoacoustic effect are nonlinear. The nonlinear response causes the phase lag in the acoustic signal to be dependent on the intensity as well as modulation frequency of the incident radiation. Additional phase shifts are caused by heat release from thermalization of the recoil energy of the nascent photofragments and an increase in mole number immediately following photofragmentation. To test the calculated amplitude and phase dependences of the optoacoustic effect produced by photodissociation, experiments with Cl/sub 2/ irradiated at a wavelength of 488 nm were done in a nonresonant spectrophone cell. Several effects depending on modulation frequency and radiation intensity were found that are characteristic of the mechanism of energy release in the system. At low frequencies the acoustic phase lag increases with modulation frequency but decreases with light intensity. At high modulation frequencies the component of the acoustic signal from the mole number increase and photofragment recoil dominates the response giving a phase lag that decreases with increasing modulation frequency. 36 references, 7 figures.

• Research Organization: Brown Univ., Providence, RI
• DOE Contract Number: FG02-84ER13235
• OSTI ID: 6035526
• Journal Information: J. Chem. Phys.; (United States), Journal Name: J. Chem. Phys.; (United States) Vol. 81:2; ISSN JCPSA
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400500* -- Photochemistry
CHEMISTRY
CHLORINE
DATA
DISSOCIATION
ELEMENTS
EXPERIMENTAL DATA
HALOGENS
INFORMATION
INFRARED SPECTROMETERS
MEASURING INSTRUMENTS
MOLECULES
NONMETALS
NUMERICAL DATA
PHOTOACOUSTIC SPECTROMETERS
PHOTOCHEMISTRY
POLYATOMIC MOLECULES
SPECTROMETERS