Thermal energy collisions between xenon Rydberg atoms in n = 31, l > 3 states and CO2 are reported. The rate constant is derived for those collisions that result in a change in m^l. The value so obtained is similar to that obtained previously for Xe(nf) - CO2 collisions that result in a change in l. It is argued that these observations imply that collisions result in simultaneous changes in l and m^l. In addition, the influence of an applied electric field on state-changing in collisions between laser-excited Xe(nf) atoms and xenon target gas is described. The presence of the field- results in marked changes in both the rate constant for collisional state-changing and in the final state distribution. The changes can be accounted for by use of energy transfer arguments based on the "essentially-free" electron model, although the degree of spatial overlap between wavefunctions associated with the initial and final states may also be important.