COLLISIONS OF XENON (NF) RYDBERG ATOMS WITH AMMONIA

In thermal collisions between Xe(nf) Rydberg atoms and NH3 collisional depopulation of the nf state occurs through at least three distinct mechanisms: n-changing collisions, l-changing collisions, and ionizing collisions. Using selective field ionization we have measured the total collisional depopulation rate constants kd for laser-excited Xe(nf) atoms in the n range of 22 to 39. The magnitudes of kd are large, corresponding to reaction cross sections comparable to the geometric size of the Xe(nf) atom at n ∼22. In the n range of 25 to 40, Xe+ ion production provides an absolute measure of the rate constants for collisional ionization. Approximate rate constants for n- and l-changing collisions are also presented for the 31f state. In these experiments we find that the state-changing collision rate constants are fairly independent of n and are determined largely by the l-changing collisions. The collisional ionization rate constants measured are smaller than the state-changing rate constants and increase with increasing n, ranging between 0.2 and 4.6×10-7 cm3/sec for n between 25 and 40. The present results are compared to those of recent theoretical calculations. © 1980 American Institute of Physics.