IONIZATION OF HIGHLY EXCITED ATOMS BY ELECTRIC-FIELDS III MICROWAVE IONIZATION AND EXCITATION

The Monte-Carlo classical trajectory method is used to obtain the probability for microwave ionisation of atoms in states n approximately=66 in agreement with the experiments of Bayfield and Koch (1974). In addition the method displays the time evolution of excitation and ionisation processes and shows that the latter may proceed through a great variety of intermediate excitation processes. The mechanism is discussed. The probability of ionisation at time t is given by Pion(t)=(1-QT)(1-exp(- beta (t)t)) where QT is the probability of orbits which lie in invariant tori. Quantal effects are not significant for comparison with the Bayfield and Koch experiment, but they are discussed in connection with the implications of the results for multiphoton laser ionisation of low n states.