Relaxation in a Na/Na2 nozzle expansion

Atom—molecule collisions in a Na/Na₂ nozzle expansion are investigated. The atoms are marked near the nozzle exit by preparing them alternatively into the 3²S and 3²P state. The effect of collisions between these atoms and the molecules is studied far downstream the beam. We find that the internal energy distribution of the molecules depends on the internal energy of the atoms. The specific change of the internal energy distribution gives information on the energy relaxation in the nozzle expansion.