Organic molecules

Isomerization and Fragmentation of Ethylene

The dynamics of organic molecules in strong laser pulses depend sensitively on the frequency ω of the laser [1],[2]. In the figure the absorption spectrum of ethylene, C₂H_4, is presented. In the movies the (very different) relaxation dynamics for different laser frequencies ω are shown.

© ITP

(a) Isomerization

At a laser frequency of ω=6.2 eV cis-trans isomerization occurs. The resulting state is vibrationally highly excited (movie).

(b) "Fission"

At a laser frequency of 9.6 eV the C-C double bond is excited and the molecule immediatly undergoes "fission", i.e. C₂H₄ → 2 CH₂ (movie).

(c) Multifragmentation

A a laser frequency of 19.3 eV all four C-H bonds are blasted away, i.e. C₂H₄ → C₂ + 4H. The nuclear dynamics as well as the time-dependent electronic density is shown in this movie.


 

• T. Kunert, F. Grossmann, and R. Schmidt, Nonadiabatic dynamics of ethylene in femtosecond laser-pulses, Phys. Rev. A 72, 023422 (2005).

• J. Handt, T. Kunert, and R Schmidt, Fragmentation and cis-trans isomerization of diimide in fs laser-pulses, Chem. Phys. Lett. 428, 220 (2006)