
522 Measurement Techniques of Femtosecond Spectroscopy
vibration is easily analyzed through diffraction of a probe pulse by the standing
wave pattern.
10.10.3. Theoretical Framework
The same density matrix formalism as in Chapters 3 and 4 can be used to
describe impulsive stimulated Raman scattering. As in Fig. 10.20, we will con-
sider Raman transitions between a ground state |1 and a first excited state |2
of a vibrational mode with frequency ω
21
. The states |1 and |2 are infrared
inactive, i.e., there is no dipole allowed transition |1→|2. Coupling between
these two states can occur via any electronic state |. All states | connected
to |