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Aufsatz
Delocalization of a hole in van der Waals clusters: Ionization potential of rare-gas and small Hg_n clusters
(American Physical Society, 1993)
The size dependence of the ionization potential I_p(n) of van der Waals (vdW) bound clusters has been calculated by using a model Hamiltonian, which includes electron hopping, vdW interactions, and charge-dipole interactions. The charge-density and dipole-density distributions for both neutral and ionized n-atom clusters are determined self-consistently. The competition between the polarization energy of the neutral atoms surrounding a partially localized hole and the tendency toward hole delocalization in the ionized ...
Aufsatz
Theory for Optical Absorption in Small Clusters: Dependence on Atomic Structure and Cluster Size
(American Physical Society, 1994)
We present a theory which permits for the first time a detailed analysis of the dependence of the absorption spectrum on atomic structure and cluster size. Thus, we determine the development of the collective excitations in small clusters and show that their broadening depends sensitively on the tomic structure, in particular at the surface. Results for Hg_n^+ clusters show that the plasmon energy is close to its jellium value in the case of spherical-like structures, but is in general between w_p/ \wurzel{3} and ...
Aufsatz
High laser field effects in multiphoton ionization of Na_2
(1992)
Femtosecond pump/probe multiphoton ionization experiments on Na_2 molecules are performed. The dependence of the total Na^+_2 ion signal on the delay time and the intensity of the femtosecond laser pulses is studied in detail. It is observed that molecular vibrational wavepacket motion in different electronic states dominates the time dependence of the ion signal. For higher laser intensities the relative contributions from the A ^1 \summe^+_u and the 2 ^1 \produkt__g states change dramatically, indicating the ...
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Three-electron radiative transitions
(1993)
A new type of many-electron radiative transitions involving three electrons is predicted. The results of their investigation by many-body perturbation theory are presented. New spectral lines observed in the wavelength range of 37.5 to 54.0 nm by means of photon-induced fluorescence spectroscopy (PIFS) following the excitation of the Kr I 3d{^-1}np resonances are reported and compared with the predictions.
Aufsatz
Molecular photochemistry with femtosecond laser pulses
(1990)
Femtosecond laser pulses generated from an amplified coiliding pulse modelocked ring dye laser have been employed in molecular beam experiments to study the dynamics and the pathways of multiphoton induced ionization, autoionization and fragmentation of Na2 . Energy distributions of photoelectrons arising from these processes and the mass and released kinetic energy of the corresponding fragment ions are measured by time-of-flight spectroscopy.
Aufsatz
Time-resolved studies of neutral and ionized Na_n clusters with femtosecond light pulses
(1993)
The real-time dynamics of Na_n (n=3-21) cluster multiphoton ionization and fragmentation has been studied in beam experiments applying femtosecond pump-probe techniques in combination with ion and electron spectroscopy. Three dimensional wave packet motions in the trimer Na_3 ground state X and excited state B have been observed. We report the first study of cluster properties (energy, bandwidth and lifetime of intermediate resonances Na_n^*) with femtosecond laser pulses. The observation of four absorption resonances ...
Aufsatz
Femtosecond pump-probe study of the spreading and recurrence of a vibrational wave packet in Na_2
(1992)
The motion of a vibrational wave packet in the bound A(^1 \summe^+_u) electronic state of the sodium dimer is detected in a femtosecond pump/probe molecular beam experiment. For short times harmonic motion is seen in the total ion yield of Na^+_2 as a function of delay time between the two laser pulses. The spreading of the wave packet results in the loss of the periodic variation of the ion signal. For longer delay times (47 ps) the wave packet regains its initial form which is reflected in the revival structure of ...
Aufsatz
Femtosecond time-resolved molecular multiphoton ionization: the Na_2 system
(1991)
We report here the first experimental study of femtosecond time-resolved molecular multiphoton ionization.
Femtosecond pump-probe techniques are combined with time-of-flight spectroscopy to measure
transient ionization spectra of Na_2 in a molecular-beam experiment. The wave-packet motions in
different molecular potentials show that incoherent contributions from direct photoionization of a singly
excited state and from excitation and autoionization of a bound doubly excited molecular state determine
the observed ...