536 Examples of Ultrafast Processes in Matter
11.3. ULTRAFAST PROCESSES IN MOLECULES
11.3.1. Observation of Molecular Vibrations
11.3.1.1. Simple Molecules
When single atoms combine to form molecules, additional internal degrees of
freedom, such as rotations and vibrations, arise, with transients in the picosecond
and femtosecond range.
Instead of an electron moving in the field of an atom, we shall now consider
the case of an atom in a molecule. For the purpose of illustration let us consider
as specific system the I
2
molecule for which the potential curves of the electronic
states are reproduced in Figures 11.3 and 11.4. A fs pulse is used to excite the
X(ν
s = 0) → B(ν
= n) transition in the 500–600 nm wavelength range (where
ν characterizes the vibronic ...