摘要:

AbstractIn small molecules the lifetime of vibrational modes critically depends upon the energy states and the anharmonic coupling of the individual molecule. Large molecules in the statistical limit exhibit very rapid intramolecular energy redistribution (≤ 1 ps). Evidence is presented for the redistribution of vibrational energy over the Vibrational manifold of the electronic ground state. A temporary internal temperature may be assigned to the excited molecules. Intermolecular energy dissipation occurs slowlier. A time constant of approximately 10 ps is observed when probed approximately 3000 cm−1above the ground st

ISSN:0005-9021    

DOI:10.1002/bbpc.19850890303

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA, Weinheim    

年代:1985

数据来源: WILEY

摘要:

AbstractWe present femtosecond techniques allowing to generate intense optical pulses from the near UV to the near infrared and their use in the monitoring of ultrafast photochemical reactions at this same time scale. Chromophores embedded in micellar solution are photoionized by femtosecond UV pulses. After the charge separation (electron), photoelectrons are shown to react with water molecules in aqueous phase of micelles and are then used to trigger and monitor the first steps of electron transfer in semi‐organized micellar solution

ISSN:0005-9021    

DOI:10.1002/bbpc.19850890304

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA, Weinheim    

年代:1985

数据来源: WILEY

摘要:

AbstractWe have determined the intramolecular potential barrier as well as total activation energies of trans‐cis isomerization in the excited state of stilbene in hydrocarbons, using UV picosecond transient‐absorption Spectroscopy. The dynamics of the isomerization is compared with theoretical predictions offered by the activated barrier crossing models of Kramers, and Grote and Hy

ISSN:0005-9021    

DOI:10.1002/bbpc.19850890305

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA, Weinheim    

年代:1985

数据来源: WILEY

摘要:

AbstractPicosecond transient Spectroscopy has been used to measure excited state lifetimes ancfrspectra of Cr, Mn, Fe, Sn and Pb meso‐tetraphenylporphyrins. Excited state spectra are typical of π,π*states, and lifetimes vary from>20 ns in Cr(III) tetraphenylporphyrin to 8 ps in Mn(II). This contrasting behaviour in the transition metal porphyrins is interpreted as being due to charge transfer states lying above the initially excited states in Cr but below those in Mn and Fe, as recently predicted by theory. Only in Sn(IV) tetraphenylporphyrin was the singlet‐singlet absorption spectrum measurable; the excited singlet state lifetimes for the other porphyrins were

ISSN:0005-9021    

DOI:10.1002/bbpc.19850890306

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA, Weinheim    

年代:1985

数据来源: WILEY

摘要:

AbstractThere are complex mechanisms which underlie the apparently simple processes of molecular dissociation and radical recombination in dense fluids. In this paper we consider aspects such as the role of metastable deep electronic traps and electronic surface hopping. The result is an analytic model which predicts trap lifetimes and bimolecular recombination rates of iodine over a range of fluid densities from low density gas phase to liquids under high pressure. The inputs into the model are simply the potential surfaces and the friction which governs the motion of an isolated atom in the fluid.

ISSN:0005-9021    

DOI:10.1002/bbpc.19850890307

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA, Weinheim    

年代:1985

数据来源: WILEY

摘要:

AbstractPhotolysis quantum yields and atom recombination rate constants were measured for iodine and bromine at pressures of up to 7 kbar in both the dense gas and liquid phase employing a variety of solvents. The results are analyzed in terms of a simple model which uses empirical parameters to describe cage break‐out, competition between diffusive separation of atom pairs and cage energy relaxation, and stabilization in halogen molecule‐solvent clusters. This enables us to single out the dominant processes governing escape versus recombination efficiencies in the different density regi

ISSN:0005-9021    

DOI:10.1002/bbpc.19850890308

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA, Weinheim    

年代:1985

数据来源: WILEY

摘要:

AbstractSpectra and rate constants of reactions were measured of chlorine and bromine atoms formed by photolysis of aqueous solutions of hypochlorous and hypobromous acids and their salts with light of wavelength 248. 5 and 308 nm. Chlorine and bromine atoms in aqueous solution behave like weak oxygen acids showing the pKa‐values 5.1 and 10.5, respectively. Exchanges of water molecules bound to the halogen atoms are fast processe

ISSN:0005-9021    

DOI:10.1002/bbpc.19850890309

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA, Weinheim    

年代:1985

数据来源: WILEY

摘要:

AbstractThe photodissociation of jet cooled H2O in the first absorption band is studied at 157 nm with an F2excimer laser. The nascent OH product state distributions are analyzed by LIF. A highly selective, strongj‐dependentΛ‐doublet population is found. A quantitative explanation of the A‐doublet selectivity is given in terms of orientation effects of the unpaired pπ‐lobe in OH. The strong inversion between theΛ‐doublet states yields a pumpmechanism for astronomic

ISSN:0005-9021    

DOI:10.1002/bbpc.19850890310

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA, Weinheim    

年代:1985

数据来源: WILEY

摘要:

AbstractThe two photon photodissociation of H2O, D2O (C̃1B1) from individually selectedJ'Ka'Kc'rotational levels in the (000) vibrational level has been investigated experimentally using a line‐narrowed, tunable KrF laser. The results establish a strong dependence on the magnitude of 〈Ja'2〉1/2≅Ka', both for the heterogeneous predissociation path and for the subsequent branching on the β1'A1potential at the Renner‐Teller intersection with Ã1B1ne

ISSN:0005-9021    

DOI:10.1002/bbpc.19850890311

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA, Weinheim    

年代:1985

数据来源: WILEY

摘要:

AbstractThis article highlights the utility of multiphoton ionisation Spectroscopy to studies of the predissociation dynamics of Rydberg states in small polyatomic molecules. Predissociation from various of the excited states of H2O, H2S and their respective deuterated analogues is demonstrated to be a sensitive function of parent rotational level and to be critically affected by H ↔ D isotopic substitution and by accidental near resonances with more heavily predissociated “doorway” states which provide more efficient coupling into the background continuum of dissociative l

ISSN:0005-9021    

DOI:10.1002/bbpc.19850890312

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA, Weinheim    

年代:1985

数据来源: WILEY