The photodissociation of Kr+n (3≤n≤11) cluster ions is observed for the first time in the 565 to 630 nm wavelength range. Kr+3 has a photodissociation cross section of (8.1±0.8)×10−17 cm2 at 612 nm, while Kr+4 and Kr+5 are found to have larger photodissociation cross sections than Kr+3 with a slightly red-shifted spectrum. Only Kr+ is detected as a photofragment of Kr+3, while in the Kr+n (4≤n≤7) experiments, both Kr+2 and Kr+ photofragments are seen. As size n increases from 7 to 11, Kr+ disappears and Kr+3 appears. Laser power studies show that all are single photon photodissociation processes. For higher order Kr+n clusters (4≤n≤7) the intensity ratio between the two photodissociation products Kr+2 and Kr+ is dependent on the wavelength of the laser light used in the photodissociation, but independent of the polarization direction of the laser. Translational energy analysis of the photofragments is used to investigate the photodissociation mechanisms. In contrast to the photodissociation of Kr+3, where two types of Kr+ photofragments with different values of translational energy release are observed, only one type of Kr+2 photofragment, with zero kinetic energy release is found in the Kr+4 photodissociation. These findings are discussed in terms of the dynamics of photodissociation and possible structures of these cluster ions.
4235the lifetime: photoi~n-photon~~ and photoelectron-photon34 coincidence measurements show the variation of the fluorescence quantum yields and the pronounced conexponen_tial decay curves as a result of coupling between the A22+ and B2ni states. The vibronic levels above the intersection point seem to be accurately described in the adiabatic approximation, at least in this case. This might be an explanation for the resolved v, and v3 vibrational modes above 13.56 eV. According to the calculations of Cederbaum et a1.I8 the inclusion of totally symmetric modes in describing diabatic effects is crucial, as they lower the minimum of the locus of intersection, thus enhancing the mixing of states. ConclusionHigh-resolution PE spectra of the three lowest system of BrCN and ICY have enabled us to reveal spin-orbit coupling net only in the X(211i) but also in the vibrationally complicated B(211i) (33) Castelluci, E.; Braitbart, L.; Dujardin, G.; Leach, S. Furuduy Discuss. Chem. Soc. 1983. 75. 90. . ~ ~~~ ~ ~~ (34) Maier, J.' PJ'Ochsner, M.; Thommen, F. Faraday Discuss. Chem. SOC. 1983, 75, 11.systems. In addition, the results have shed more light on some phenomena that cannot be understood if conventional FranckCondon principle were valid. The high-resolution spectra of the 211i and 2Z+ systems indicate the activity of the bending mode ( v 2 (~) ) .It gains intensity through vibronic mixing either within or between states of proper symmetry. The strength and importance of such diabatic effects is dependent on energy separation. If the separation is much greater than the energy of the inducing normal mode, the vibrational pattern can still be analyzed wiLhi_n the adiabatic approximation, as seems to be the case in the A/B systems of BrCN. However, it is expected to lead to complete breakdown of the vibrational progression in that part of the spectrum which corresponcis io the closely spaced electronic systems, as observed in the A/B systems of ICN. According to the Heidelberg group'* the role of the totally symmetric modes in bringing about such nonadiabatic effects is crucial.Acknowledgment. The author thanks Prof. L. Klasinc for drawing her attention to the problem and Prof. T. Cvitai for careful reading of the manuscript. This work was supported by the Republic Council for Science (SIZ-2) of S.R. Croatia.Frequencies of 60 a-type R-branch rotational transitions were measured for e-caprolactone. Rotational constants derived from the data for the cis-chair conformation were 3201.25 & 0.05, 1920.51 f 0.05, and 1348.73 f 0.05 MHz. Higher energy conformations were not observed, in agreement with predictions of molecular mechanics calculations. Observation of vibrational satellites for a number of lines indicates a small-amplitude, low-frequency vibration.
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