摘要:

AbstractMolecular beam techniques for study of collisional and spectroscopic processes have recently been enhanced by use of static electric or magnetic fields to orient or align molecules with permanent dipole moments. A more general method is now in prospect, applicable both to alignment and to spatial trapping of molecules. This exploits the anisotropic interaction of the electric field vector of intense laser radiation with the dipole momentinducedin apolarizablemolecule by the laser field. The interaction creates directional superpositions of field‐free states that correspond to oblate spheroidal wavefunctions, with eigenenergies that decrease with increasing field strength. We suggest that this polarizability interaction produces the marked alignment found in laser‐induced dissociative ionization of CO by the Saclay group. We also present calculations illustrating the feasibility of spattal trapping. In combination with supermirror focussing and buffer‐gas cooling, an intense infrared laser can typically confine molecules for long‐times (‐hours) within a small (‐picoliter) and cold (−1°K) “

ISSN:0009-4536    

DOI:10.1002/jccs.199500020

出版商:WILEY‐VCH Verlag    

年代:1995

数据来源: WILEY

摘要:

AbstractWe report the development of a novel hard X‐ray diffraction system with picosecond time resolution. Picosecond X‐ray pulses are produced by excitation of an X‐ray diode with picosecond ultraviolet light pulses at a repetition rate of 300 Hz. The X‐ray pulses are synchronized to the optical pulses with picosecond accuracy. The system has been utilized in picosecond time resolved X‐ray diffraction of laser pulse heated gold and platinum single

ISSN:0009-4536    

DOI:10.1002/jccs.199500021

出版商:WILEY‐VCH Verlag    

年代:1995

数据来源: WILEY

摘要:

AbstractResults of our femtosecond‐picosecond laser photolysis studies on photoinduced electron transfer phenomena in solutions including exciplex dynamics and its solvent dependences, energy gap dependences of photoinduced charge separation and charge recombination of various geminate ion pairs, mechanisms of chemical reactions via exciplexes and ion pairs, dynamics of photoinduced election transfer in hydrogen bonding complexes, dynamics and mechanisms of photoinduced electron transfer in fixed distance donor acceptor dyads and photosynthetic reaction center models, and mechanisms of electron ejection from solute fluorescent state in polar solutions are summarized and discusse

ISSN:0009-4536    

DOI:10.1002/jccs.199500022

出版商:WILEY‐VCH Verlag    

年代:1995

数据来源: WILEY

摘要:

AbstractWe explore in detail the nature of the intermolecular interactions in two HF containing complexes, ArHF and N2HF, at vibrationally excited HF stretching states using both high overtone spectroscopic andab initiocomputational methods. By using an infrared intracavity laser‐induced fluorescence technique, second overtone spectra of the two HF complexes have been obtained for the HF stretches and their combination modes with low‐frequency van der Waals vibrations. The two complexes show the same trend that both van der Waals bond strength and rotational constant increase smoothly with v of the HF stretch. The investigation of the intermolecular potential above minimum provides a rigorous test ofab initiocalculations. In particular for theab initiocalculations using an efficient basis set incorporating bond functions, the technique reproduces reasonably well the anisotropy of the interaction potential of Ar and HF. It is found that the intermolecular potential depends strongly upon the HF bond length only at the linear Ar‐H‐F g

ISSN:0009-4536    

DOI:10.1002/jccs.199500023

出版商:WILEY‐VCH Verlag    

年代:1995

数据来源: WILEY

摘要:

AbstractThe dynamics of S(3P2,1,0;1D2;1S0) production from the 193 nm photodissociation of CH3SH has been examined by 2+1 resonance‐enhanced‐multiphoton‐ionization (REMPI) techniques. Using the rate equation scheme, we have rationalized the intensities of S(3P2,1,0;1D2;1S0) observed according to the sequential two‐photon dissociative pathways, (A): CH3SH + hv (193 nm) → CH3S + hv (193 nm) → S and (B): CH3SH + hv (193 nm) → HS + hv (193 nm) → S, as the major mechanisms for S production. We have satisfactorily fitted the photodissociation laser power dependencies for S(3P) and S(1D) produced from CH3SH by invoking photodissociation cross sections and branching ratios S(3P)/S(1D) for CH3S and HS similar to those determined previously in the 193 nm photodissociation of CH3SCH3and H2S. This observation supports that the 193 nm photodissociation of CH3S and HS prepared from CH3SH yield predominantly S(lD) and S(3P), similar to the cases for CH3S prepared from CH3SCH3and for HS prepared from H2S, respectively. A small amount of S(1S0) observed from the 193 nm photodissociation of CH3SH is attributed

ISSN:0009-4536    

DOI:10.1002/jccs.199500024

出版商:WILEY‐VCH Verlag    

年代:1995

数据来源: WILEY

摘要:

AbstractIn this paper we present two recent studies utilizing pressure tuning spectroscopy. In the first of these we use high pressure photoluminescence to characterize the large difference in luminescence efficiency at one atmosphere between [Ru(bpy)3]2+and [Ru(bpy)2py2]2+ions. The lower efficiency of the latter ion is due to dissipation of excitation energy by motion of the pyridines.The second study involves a combination of photo‐and thermoluminescence of doped ZnS phosphors of technical importance. In the phosphor doped with CI and Cu+we demonstrate that the donors are pinned to the conduction band and the acceptors to the valence band. We invoke the presence of “deep levels” to describe the behavior of the traps. In the phosphor doped with Mn+2plus C1‐ and Cu+a series of traps appeared as the pressure was increased. By comparison with ZnS doped only with Mn+2it was possible to assign some of the traps to C1‐ and other

ISSN:0009-4536    

DOI:10.1002/jccs.199500025

出版商:WILEY‐VCH Verlag    

年代:1995

数据来源: WILEY

摘要:

AbstractRotationally inelastic collisions of NH2( Ã2A1), ∑(0,9,0), 303, 101have been studied by measuring the dispersed fluorescence spectra at molecular beam conditions. The results show that the angular momentum transfer rule is much more successful than is that predicted by energy gap law for fitting the rotational energy transfer rate. For ΔN<2 the transfer rates are getting slow down. Downward transfer rates are faster than those of upward transfer. With same angular momentum transferred, the transfer rates for Δka= 0 process are larger than those for Δka≠0. It is also found that rotation transfer process is a very efficient way for decaying of the initially pumped levels. About 60% of the initially pumped 303is colliding into other rotational levels. Energy transfer reactions of metastable rare gas atoms (Rg*) with N2, NH3, CS2were investigated by measuring the emission spectra. The preferential population of n(A″) of NH(c1II) was found in He(23S) + NH3reaction, the experimental data shows II(A″)/II(A′) = 1.2 at J′<13. A high vibrational excitation and low rotational excitation of N2(C3n) were observed in Ne(3P02) + N2reaction comparing with Ar(3P0.2) + N2reaction. The detailed vibrational populations of CS2+(Ã, B̃) achieved by He(23S)/Ne(3P0.2) + CS2reaction are different from those obtained by PES. The vibrational distributions of CH(A2Δ) obtained by He(23S) + CHC13(CH3NO2) reactions were discussed based on statistical theory, special attention was paid to reveal the role played by tie angular momentum restriction in this process. The result on energy transfer between N2(a1Π) and CO(X1∑) was firstly presented by VUV emission spectra at single collision condition. The mechanisms of energy transfer related to some of the reactions mentioned above were also

ISSN:0009-4536    

DOI:10.1002/jccs.199500026

出版商:WILEY‐VCH Verlag    

年代:1995

数据来源: WILEY

摘要:

AbstractIn this paper, we review the generalized Forster‐Dexter theory to treat photoinduced electronic energy transfer for a system in dense media and for an isolated system (i.e., a system in the collision‐free condition). Instead of expressing the rate of energy transfer in terms of spectral overlap, the expression of the energy‐transfer rate constant is obtained by evaluating a Fourier integral involved in the energy transfer rate constant using the saddle‐point method. In this way, the energy‐gap dependence, and the effect of temperature and the isotope effect on the energy transfer can be easily studied. The effect of bridge groups connecting between donor and acceptor chromophores on the intramolecular energy transfer is als

ISSN:0009-4536    

DOI:10.1002/jccs.199500027

出版商:WILEY‐VCH Verlag    

年代:1995

数据来源: WILEY

摘要:

AbstractThe three‐level system subjected to electromagnetic fields is investigated. It is shown that when one of two fields is strong (the pumping field), the system can amplify the second (probe) field even if no population inversion is created, but some phase relations are satisfied. The conditions necessary for inversionless amplification to take place are discussed. The connection between this effect and stimulated Raman emission is shown. Numerical simulations for each one of the discussed cases were performe

ISSN:0009-4536    

DOI:10.1002/jccs.199500028

出版商:WILEY‐VCH Verlag    

年代:1995

数据来源: WILEY

摘要:

AbstractIt is the purpose of this work to give a theoretical description of the role played by the Duschinsky rotation in sum frequency generation experiments performed on adsorbed molecules. In addition to the mode mixing resulting from the Duschinsky rotation, frequency shifts as well as nuclear equilibrium position shifts, occuring under electronic excitation, are incorporated in the present model. The sum frequency generation spectra are calculated in order to compare the effects of the equilibrium position shifts and the quadratic mode mixing.

ISSN:0009-4536    

DOI:10.1002/jccs.199500029

出版商:WILEY‐VCH Verlag    

年代:1995

数据来源: WILEY