State changing collisions

State changing collisions between singly charged positive ions and Rydberg atoms of Na have been studied extensively using crossed beams of atoms and ions, the approach shown in Fig. 13.1.1 The Na atoms in a thermal beam are excited to a... 

While electrons in conventional beams have velocities too high to have large cross sections, thermal electrons have large cross sections for state changing collisions with Rydberg atoms, and these collisions have been studied in a systematic fashion. Specifically, metastable He atoms in a stationary afterglow have been excited to specific Rydberg states with a laser.37 38 The populations of... 

Avdeenkov and Bohn also studied ultracold collisions between OH [135,136] and OD radicals [137] in the presence of an applied electric field. They showed that elastic scattering is more efficient than inelastic processes for ultracold collisions between fermionic OD molecules [137], inhibiting state-changing collisions. The energy dependence of elastic and inelastic cross-sections for OH + OH and OD + OD collisions is illustrated in Figure 3.24 for an applied electric field of e = lOOV/cm. While the elastic cross-sections approach finite values in the Wigner regime for the bosonic system of OH molecules and the fermionic system of OD molecules, the... 

Seemingly this route is not very efficient because only molecules in a particular rotational level can be pumped up. If the rotational spacing 2B is small, many rotational states ate populated in a thermal sample at room temperature. They will not absorb. But if rotational spacing is large, we diow in Chapter 9 that rotational-state-changing collisions are very efficient. So in the bulk, molecules in a given j absorb and are pumped up. This upsets the rotational state equilibrium and collisions restore the population in level j. These molecules absorb, and so on. Hence, in the bulk, many molecules are efficiently heated. 

Eq. (7.11)) of the rate constant kq for state-changing collisions of HCI with Kr. The very high rates of rotational state changes, cf. 

State-changing collisions molecular energy transfer... 

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