Berlin 2005 – scientific programme

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MO: Molekülphysik

MO 23: Femtosecond Spectroscopy

MO 23.3: Talk

Saturday, March 5, 2005, 14:30–14:45, HU 2091

Photoionisation dynamics of longchained alcohols and alkanes — •Martin K. Fischer, Andy Thaller, and Alfred Laubereau — Technische Universität München, Physik-Department E11, James-Franck-Strasse, D-85748 Garching

The photoionization process of the longchained molecules dodecane and decanol is compared to study the effect of hydrogen bonding in electron trapping process. The relaxation dynamics are investigated after two photon excitation at 9.2 eV (pump 270 nm) in a large spectral range from 450 nm to 5.2 µm.

The transient absorption spectra measured in decanol show two separate absorption bands: The well known absorption band of an electron in a solvation shell of O-H-groups and a notable absorption band in the near IR at around 0.6 eV not reported previously. To identify this feature as a new kind of trap, investigations in a comparable alkane are conducted. In fact, in dodecane an absorption with the same dynamics and very similar spectral features can be observed. As a result the absorption can be clearly assigned to a solvated electron localized in a shell of C-H-groups.

A comparison of the results on decanol with dodekane and methanol is presented. Clear evidence is provided for the existence of two different electron traps in decanol formed on the one hand by O-H-groups of the alcohol as in methanol and, on the other hand by C-H-groups of the alkylic part as in dodecane.