Photodissociation of methylnitrite in the vacuum ultraviolet. I. Identification and quantum yields of electronically excited NO products

1980 ◽  
Vol 73 (3) ◽  
pp. 1187-1192 ◽  
Author(s):  
F. Lahmani ◽  
C. Lardeux ◽  
M. Lavollée ◽  
D. Solgadi
Keyword(s):  
Vacuum Ultraviolet ◽  
Quantum Yields ◽  
Electronically Excited

The Vacuum Ultraviolet Photolysis of Cyclopentanone

1972 ◽  
Vol 50 (24) ◽  
pp. 3938-3943 ◽  
Author(s):  
Alfred A. Scala ◽  
Daniel G. Ballan
Keyword(s):  
Quantum Yield ◽  
Carbonyl Group ◽  
Incident Energy ◽  
Vacuum Ultraviolet ◽  
Quantum Yields ◽  
Electronically Excited ◽  
Ultraviolet Photolysis

In the vacuum ultraviolet photolysis of cyclopentanone, the major modes of fragmentation of the electronically excited ketone are:[Formula: see text]The sum of the quantum yields for reactions A and B is 0.87 at 147.0 nm and these reactions become less important as the incident energy is increased. A pressure study at 147.0 nm of the partitioning of the tetramethylene diradical between paths A and B indicates that the ratio kA/kB is approximately 8. The quantum yield for reaction 8 is only 0.02. The remainder of the decomposition of cyclopentanone is accounted for by reactions 4 and 5, which appear to become more significant as the incident energy increases. The mechanisms for reactions 6 and 8 are best interpreted in terms of diradicals of structure (CH2)n where n = 1, 3, and 4. The lack of non-acyl σ-cleavage at 147.0 nm is an indication that the absorption of energy occurs at the carbonyl group.

Molecular Vibrations in the Exciton Theory for Molecular Aggregates. V. Electronic Spectra of Weakly-coupled Systems

1963 ◽  
Vol 16 (3) ◽  
pp. 315 ◽  
Author(s):  
EG McRae
Keyword(s):  
Electronic Spectra ◽  
Fluorescence Spectra ◽  
Vibrational Structure ◽  
Coupled Systems ◽  
Quantum Yields ◽  
Molecular Aggregates ◽  
Relative Quantum ◽  
Electronically Excited ◽  
Anthracene Crystal ◽  
Theoretical Results

The theory of the gross vibrational structure in the electronic spectra of molecular aggregates is developed for the case of weak intermolecular interaction. The electronically excited states are represented by a set of m-m functions corrected to first order as described in Part IV of this series. An explicit treatment is given for aggregates with two molecules per unit cell. Formulae are obtained for the relative vibronic intensities, splittings, and polarization ratios in absorption spectra, and for relative quantum yields and polarization ratios in fluorescence spectra. The theoretical results are compared with those of the E-V coupling theory developed in Parts II and III. On the basis of this comparison, a general equation is put forward to relate the theoretical crystal splitting (i.e. the splitting for a rigid model) to observed polarization ratios in spectra. The theoretical results are compared with the observed vibrational structure in the 3800 Ǻ band system of anthracene crystal. The crystal splitting calculated from the observed polarization ratios is 380 cm-1. The theory accounts, within the rather large experimental error, for the observed variations of polarization ratio in both the absorption and the fluorescence spectra of anthracene crystal.

Photochemistry of acetylene

1983 ◽  
Vol 61 (5) ◽  
pp. 850-855 ◽  
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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