No abstract

The gas-phase vibrational spectroscopy of cold C N (n=2-4) anions is investigated in the CC and CN multiple bond stretching region (1700-2250 cm ) by means of infrared photodissociation (IRPD) spectroscopy in a cryogenically cooled ion trap of the corresponding messenger-tagged complexes. The IRPD spectra are assigned to N-terminated linear structures with triplet ground states ( Σ ) based on a comparison with harmonic vibrational frequencies and intensities from density functional theory computations. In contrast to the polyacetylenic C N anions, the linear C-C chains investigated here exhibit cumulenic character, which is most pronounced in C N and decreases with chain length. Additional intense transitions are observed for C N above 3000 cm and are attributed to overtone and combination bands involving the CC stretching modes, based on anharmonic computations. The influence of a D tag on the vibrational features of C N anions is shown to be small.

No abstract

The photofragmentation of Cu 3 and Al 4 clusters during charge reversal with white-light pulses is optimized by using an evolutionary algorithm and a pulse shaping setup. By controlling the spectral phase over the full spectral range of the supercontinuum, tailored pulses are generated with the aim of adapting the energetic and temporal structure of the pulse to the characteristic dynamics and electronic manifold of the investigated systems. In this context, maximizing the ratio of the cationic yield of a selected fragment (Cu 2 + and Al + ) and the parent ion is chosen as an optimization target. Significant enhancement factors are achieved, demonstrating a high selectivity in populating specific points on the potential energy surface, which facilitates the targeted photofragmentation of the investigated systems. The optimal pulse shapes indicate that both vibronic as well as electronic wave packets are probed. Additional laser-induced dissociation experiments suggest that fragmentation of the Cu 3 clusters occurs in an excited state of the neutral species. Further photofragmentation studies of the Cu 3 − anions present a strong wavelength dependence, with the formation of Cu − occurring only when irradiated with wavelengths shorter than 528 nm. No photodissociation is observed for the Al 4 − anions.

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