1. Dissipation and Coherence: Halogens in Rare Gas Solids Signatures of Dissipation in Pump-Probe Spectra Dissipation of Energy in Excited Halogens Dispersion and „Decoherence“: Classical vs. Quantum Effects New Experiments with Phase-Locked Pulses M. Bargheer, M. Gühr, P. Dietrich, M. Fushitani, T. Kiljunen and N. Schwentner Institut für Experimentalphysik

2. Diatomics in Solid Rare Gas I 2 in Kr Fcc lattice, closest packing Adiabatic dynamics including dissipation are well described in classical simulations strong coupling to „solvent“ some similarities to gas phase

3. Energy loss from oscillations Bargheer et al., PCCP 4, 75 (2002)

4. Energy loss from signal envelope

5. Vibrational relaxation of I 2 /Kr

6. Vibrational relaxation of I 2 /Kr, ClF/Ar and Cl 2 /Ar

7. Collisions Cause Coherence? Collision of I 2 with surrounding Kr Width of wavepacket: 500 cm -1 Energy loss in collision: 1500 cm -1 Collision populates new vibrational levels coherently! well defined timining of collision well defined scattering geometry!

8. Mechanisms of „Dephasing“ Decoherence due to collisions with solvent(pure dephasing T 2 ´) Population decay by vibrational relaxation (and non-adiabatic couplings)(relaxation time T 1 ) Dispersion due to anharmonicity(dispersion time T disp ) R Energy  

9. Dispersion: Classical and Quantum Effects Compensation of dispersion by negative chirp of excitation pulse Classical! Rephasing of wavepacket after dispersion Rephasing time T rep = 1/  e x e (after dispersion of the packet) discrete vibrational levels needed

10. Dispersion in Morse-Potential (Classical) Morse-potential: Frequency: R   T1T1 T2T2  T = n(T 1 - T 2 ) Dispersion-time: (wave packet width  T > 1/2T morse ) Energy

11. Dispersion of I 2 -Wave-Packets T disp = 2 ps T disp = 5 ps If N = number of excited vibrational levels:

12. Dispersion of ClF-Wave-Packets T disp < 1 ps

13. Experiments with Phase-Locked Pulses Generation of Pulse-Pairs: Constructive Interference Destructive Interference Scherer et al., J. Chem. Phys. 95, 1487 (1991) Piezo Piezo tunes phase by moving distance /2

14. Explanation in Frequency Domain Pulse-Pairs in frequency domain yield spectral interferences, if pulses overlap. Frequency resolution of monochromator broadens pulses. Observed signal: Fluorescence, i.e. integrate from -∞ to +∞ Vibrational states act as a monochromator => interference constructive destructive no interference

15. Phase-Locked Pulses in the Presence of Dissipation: Proposed Experiment: Cl 2 in Ar Phonon side-bands increase for higher vibrational levels Excitation of zero-phonon lines => oscillation of free molecule? Cl 2 / Ar Excitation of phonon sidebands => dissipative dynamics Coherent control of dissipative vs. free wave packet motion constructive destructive no interference

16. Summary Signatures of relaxation Energy loss of halogens in Rg Collisions cause coherence Dispersion in anharmonic potentials Experiments with phase- locked pulse pairs 012345 0.0 0.2 0.4 0.6 0.8 1.0 simulated signal t / ps 10 states 4 states