Nanosecond and picosecond laser flash photolysis studies of 2,2′-dinitrodiphenylmethanes

1993 ◽  
Vol 70 (3) ◽  
pp. 245-251 ◽  
Author(s):  
T. Mathew ◽  
D. Ramaiah ◽  
C.P. Joshua ◽  
D. Weir ◽  
M.V. George
Keyword(s):  
Flash Photolysis ◽  
Laser Flash Photolysis ◽  
Picosecond Laser ◽  
Laser Flash

Primary photochemical events in CdS semiconductor colloids as probed by picosecond laser flash photolysis

1989 ◽  
Vol 157 (5) ◽  
pp. 384-389 ◽  
Author(s):  
Prashant V. Kamat ◽  
Thomas W. Ebbesen ◽  
Nada M. Dimitrijević ◽  
A.J. Nozik
Keyword(s):  
Flash Photolysis ◽  
Laser Flash Photolysis ◽  
Picosecond Laser ◽  
Laser Flash

Time-resolved nanosecond and picosecond absorption studies of excited-state properties of 1-thiobenzoylnaphthalene

1989 ◽  
Vol 67 (6) ◽  
pp. 967-972 ◽  
Author(s):  
R. Minto ◽  
A. Samanta ◽  
P.K. Das
Keyword(s):  
Rate Constants ◽  
Flash Photolysis ◽  
Laser Flash Photolysis ◽  
Picosecond Laser ◽  
Laser Flash ◽  
Quantum Yields ◽  
Pulse Excitation ◽  
Nanosecond Laser Pulse ◽  
Nanosecond Laser ◽  
Quenching Rate

1-Thiobenzoylnaphthalene (TBN), known for its pericyclization reaction from the lowest excited singlet state (S1), has been subjected to nanosecond and picosecond laser flash photolysis studies. The two major transients observed in the course of nanosecond laser pulse excitation are (i) the short-lived triplet characterized by two absorption maxima (400–410 and 740–750 nm) and submicrosecond intrinsic lifetimes (80–130 ns) and (ii) a relatively long-lived species (λmax = 520 nm and τ = 220–240 ns). Various triplet-related photophysical data of TBN, including self-quenching and bimolecular quenching rate constants, have been determined. The existence of a photochemical path from S1 manifests itself in low intersystem crossing quantum yields, particularly in the polar/hydrogen-bonding solvent, methanol. From the build-up of the triplet under picosecond excitation into S1 the lifetime of the latter is estimated to be ≤ 50 ps (in benzene). The fast intrinsic decay of TBN triplet is attributable to facile intra- and intermolecular photochemistry. The 520 nm transient species could not be definitively assigned, except that it is neither a triplet nor a triplet-derived product and that it arises via photochemistry from S1. Keywords: laser flash photolysis, triplet, transients, absorption maxima, lifetimes, quenching rate constants, photochemistry, 1-thiobenzoylnaphthalenes.

Transient intermediates in the photolysis of iodonium cations

1987 ◽  
Vol 65 (10) ◽  
pp. 2342-2349 ◽  
Author(s):  
R. J. Devoe ◽  
M. R. V. Sahyun ◽  
N. Serpone ◽  
D. K. Sharma
Keyword(s):  
Flash Photolysis ◽  
Laser Flash Photolysis ◽  
Charge Transfer Band ◽  
Picosecond Laser ◽  
Laser Flash ◽  
Allowed Transition ◽  
Phenyl Cation ◽  
Transient Intermediates ◽  
Dissociative State ◽  
Picosecond Laser Photolysis

Pulsed picosecond laser photolysis of the diphenyliodonium cation indicates that excitation of the allowed transition is followed by rapid (ps) deactivation to a homolytically dissociative state, presumably T1. Steady-state photolysis yields iodobenzene and biphenyl from the primary radical products. Iodobiphenyl is also observed. We infer in-cage recombination of these radical products, with intervention of a carbocationic intermediate. Laser flash photolysis of diphenyliodonium iodide in its charge transfer band yields an initial transient with a lifetime of ca. 200 ps. A strongly absorbing secondary transient is observed on the nanosecond time scale. Iodobenzene is the exclusive reaction product. We infer that it is not formed directly from the primary photoproduct, but through in-cage recombination of phenyl cation with iodide anion, as in benzenediazonium iodide.

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