Femtosekundenspektroskopie von Silberatomen in einer Xenonmatrix

Die elektronische Anregung des 5s-5p-Uberganges von Ag-Atomen, die in einer Xe-Matrix isoliert sind, fuehrt zu einer dynamischen Jahn-Teller Aufspaltung, die zusaetzlich zu der schon in der Gasphase auftretenden Spin-Bahn Aufspaltung, eine weitere Aufhebung der Entartung des angeregten p-Zustandes bedingt. Die Dynamik auf diesen Jahn-Teller Potentialflaechen und die Schwingungsrelaxation, die zu stark Stokes verschobenen Emissionsbanden fuehrt, wurde mit ultrakurzen Pulsen um 170 fs untersucht. Die zur Untersuchung benotigten ultrakurzen Pulsen um 660 nm bzw. 330 nm mit Energien im mJ-Bereich wurden in einer Kombination aus einem kommerziellen Titan-Saphir-Ultrakurzpulslasersystem und einem selbstgebauten Farbstofflaser erzeugt und anschliessend in einem FROG-Aufbau charakterisiert. Die Wellenpaketdynamik wurde mit Hilfe der resonanten Pump-Probe Spektroskopie untersucht und dabei 1.3 ps nach Anregung in die oberen Zustande des Tripletts eine Erhoehung im Signal beobachtet. Eine theoretische Modellierung zeigt, dass diese Erhoehung als Rekurrenz des Wellenpaketes interpretiert werden kann Ergaenzend wurde die Zwei-Farben Fluoreszenzverlustspektroskopie eingesetzt, um die Dynamik waehrend der Relaxation in die Minima der angeregten Jahn-Teller Zustaende zu verfolgen. In dem hier vorgestellten System Ag/Xe dominiert jedoch die Absorption in hoehere elektronische Zustaende und minimiert als Folge dessen die Ausbeute der stimulierten Emission. Ein wichtiges Ergebnis der Zwei-Farben Messung war die Bestimmung des ionischen Zustandes des Ag-Atomes in der Xe-Matrix bei 5.73 eV.The excitation of the s-p transition of single Ag atoms in a Xe matrix leads to a dynamical Jahn-Teller splitting which, in addition to the spin-orbit coupling removes the degeneracy of the excited p-orbital. The dynamics on these Jahn-Teller surfaces and the vibrational relaxation responsible for the strongly Stokes shifted emission bands are studied using pulses with 170 fs time resolution. The pulses with wavelengths around 660 nm and 330 nm and energies in the mJ-range are generated combining a commercial Titan-Sapphire laser system with a self-designed dye amplifier and are analzyed in a FROG setup. The wave packet dynamics is investigated by means of one-colour resonant pump-probe measurements that show an increase of the signal 1.3 ps after the excitation into the upper two states of the triplet. Simulations of the wave packet dynamics in the excited states support the interpretation of this increase in terms of a returning wave packet. Two-colour fluorescence depletion experiments are used to study the dynamics during the relaxation process toward the minima in the excited Jahn-Teller states. For Ag atoms in a Xe matrix the process is dominated by the absorption in energetically higher-lying states with a consequent reduction of the stimulated emission yield. An important result of these measurements is the determination of the energy of an Ag-ion state in the Xe at a value of 5.73 eV.SIGLEAvailable from: http://www.iwi-iuk.org/dienste/TheO/ / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDEGerman

Femtosecondspectroscopy of silver atoms in a xenon matrix

The excitation of the s-p transition of single Ag atoms in a Xe matrix leads to a dynamical Jahn-Teller splitting which, in addition to the spin-orbit coupling removes the degeneracy of the excited p-orbital. The dynamics on these Jahn-Teller surfaces and the vibrational relaxation responsible for the strongly Stokes shifted emission bands are studied using pulses with 170 fs time resolution. The pulses with wavelengths around 660 nm and 330 nm and energies in the mJ-range are generated combining a commercial Titan-Sapphire laser system with a self-designed dye amplifier and are analyzed in a FROG setup. The wave packet dynamics is investigated by means of one-colour resonant pump-probe measurements that show an increase of the signal 1.3 ps after the excitation into the upper two states of the triplet. Simulations of the wave packet dynamics in the excited states support the interpretation of this increase in terms of a returning wave packet. Two-colour fluorescence depletion experiments are used to study the dynamics during the relaxation process toward the minima in the excited Jahn-Teller states. For Ag atoms in a Xe matrix the process is dominated by the absorption in energetically higher-lying states with a consequent reduction of the stimulated emission yield. An important result of these measurements is the determination of the energy of an Ag-ion state in the Xe at a value of 5.73 eV

ULTRAFAST WAVE PACKET DYNAMICS IN JAHN-TELLER SURFACES; Ag ATOMS TN Xe CRYSTALS

Author Institution: Fachbereich physik, FU BerlinThe dynamics on Jahn-Teller surfaces involving pseudorotation, radial oscillations and the symmetric breathing mode has been already explored in isolated triatomics like $Na_{3}$. This contribution deals with the additional effects occuring in the condensed phase and originating from the energy dissipation to the lattice by phonon emission. A study with femtosecond pump-probe spectroscopy is carried out for substitutional Ag atoms in a rare gas lattice (Xe) of cubic (fcc) symmetry. Excitation from the electronic ground state with s-symmetry to the p-orbitals of the Ag atom leads to a dynamic Jahn-Teller splitting which removes the degeneracy of the p-orbitals by a coupling to nontotally symmetric phonon modes. Energy dissipation of the initially pseudorotating wave packets leads to structural relaxation and to a thermalized population in a strongly statically deformed geometry according to the large Stokes shift of about 2 eV. The initial population in the Jahn-Teller state is probed by a transient bleaching of the ground state resulting in a life time of several ps. The observed subpicosecond dynamics is related to the cubic and noncubic modes derived from MCD experiments. The subsequent energy dissipation of about 0.4 eV corresponding to 80 phonons is detected by fluorescence dip spectroscopy. The static deformation and the thermalization in it is completed in 5-7 ps. This very fast energy relaxation cannot be attributed to single phonon emission events for a phonon period of about 1 ps and is discussed with respect to higher order terms in Jahn-Teller surfaces