STUDIES OF CHEMICAL REACTIONS OF EXCITED SPECIES USING INTENSE LIGHT SOURCES

R. A. Marcus

doi:10.1139/v58-012

STUDIES OF CHEMICAL REACTIONS OF EXCITED SPECIES USING INTENSE LIGHT SOURCES

Canadian Journal of Chemistry ◽

10.1139/v58-012 ◽

1958 ◽

Vol 36 (1) ◽

pp. 102-106 ◽

Cited By ~ 3

Author(s):

R. A. Marcus

Keyword(s):

Flash Photolysis ◽

Excited Molecule ◽

Inert Gases ◽

Light Sources ◽

Adiabatic Temperature Rise ◽

Misleading Information ◽

Fluorescence Studies ◽

Excited Species ◽

Electronically Excited ◽

Intense Light

The use of measurements of the products of flash photolysis as a means for studying the reactions of electronically-excited molecules is discussed. With intense light sources the problem of isolating these reactions from others involving free radicals is simplified. The flash sources also have their limitations, and misleading information which can result from the presence of inert gases is noted. A diagnostic test is proposed for detecting the effects (if any) of a possible adiabatic temperature rise of the flash.Some recent studies in the author's laboratory are summarized. Evidence is presented that in the flash photolysis of acetone acetyl radicals arise from an excited molecule. Several deactivation processes are described and compared with results from fluorescence studies.

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The photolysis of hexafluoroacetone

Proceedings of the Royal Society of London Series A - Mathematical and Physical Sciences ◽

10.1098/rspa.1956.0051 ◽

1956 ◽

Vol 234 (1199) ◽

pp. 476-488 ◽

Cited By ~ 29

Keyword(s):

Quantum Yield ◽

Initial Step ◽

Excited Molecule ◽

Inert Gases ◽

Wide Range ◽

Electronically Excited ◽

Photolytic Decomposition ◽

Long Lifetime ◽

The Stability ◽

Excellent Source

The photolytic decomposition of hexafluoroacetone has been studied over a wide range of temperatures and pressures using light of wavelength 3130 Å. The initial step involves the production of CF 3 radicals, and the only products are C 2 F 6 and CO. The reaction is an excellent source of CF 3 radicals. The quantum yield diminishes with increasing pressure. A mechanism is suggested involving the participation of an electronically excited molecule of comparatively long lifetime, and the effect of various inert gases on the stability of this species is discussed.

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Photochemistry of acetylene

Canadian Journal of Chemistry ◽

10.1139/v83-153 ◽

1983 ◽

Vol 61 (5) ◽

pp. 850-855 ◽

Cited By ~ 27

Author(s):

H. Okabe

Keyword(s):

Quantum Yield ◽

Ground State ◽

Vacuum Ultraviolet ◽

Inert Gases ◽

Primary Process ◽

Fluorescence Studies ◽

Ethynyl Radical ◽

Absorption Of Light ◽

Electronically Excited

Photochemical and fluorescence studies of acetylene initiated by absorption of light in the vacuum ultraviolet have been described. The photochemical primary process consists of (1) the formation of C2 + H2, (2) the production of C2H + H, and (3) the formation of a metastable acetylene. The quantum yield of process (1) is about 0.1 and that of process (2) is 0.06 at 1849 Å and 0.3 at 1470 Å. The metastable acetylene either reacts with ground state acetylene to produce diacetylene or is deactivated by collisions with the walls, inert gases, or by fluorescence. A quasicontinuous emission is observed in the 4000 to 6000 Å region when acetylene is exposed to incident wavelengths below 1305 Å. This emission is ascribed to an electronically excited ethynyl radical. The rates of reaction C2H + H2 → C2H2 + H and C2H + RH → C2H2 + R (RH = CH4, C2H6, C3H8) have been measured. The photochemistry of acetylene in the Jovian and Titan atmospheres is briefly discussed.

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