Physical Chemistry 3: — Chemical Kinetics — - Christian-Albrechts ...

5.4 Advanced collision theory 117
I
Figure 5.13: Derivation of the fundamental equation.
5.4.2 Crossed molecular beam experiments
I Differential and integral reactive cross sections: Experiments with crossed molecular
beams allow us to measure differential and integral reactive cross sections
(Herschbach 1987, Lee 1987).
We consider the reaction
( )+ ( ) −→ ( )+ ( ) (5.144)
where denotes the speeds of the molecules and stands for the quantum numbers
of their energy states (electronic, vibrational, rotational, nuclear spin). In an ideal
experiment (which has yet to be performed), all of the reactants are defined by, e.g.,
a specific excitation using laser, and the of the products are determined by some
probe laser. The can be determined in a molecular beam experiment using a rotating
disk velocity selector (see Fig. 5.14).