Quantum aspects of laser-induced breakdown in argon

This paper presents a theoretical study of laser-induced breakdown in argon. It is shown that the Ramsauer minimum in the momentum-transfer cross section of argon causes the mean electron energy in the discharge to be rather small. Thus, in the case of large laser quanta, the process of breakdown must be treated quantum mechanically. In order to calculate breakdown parameters for this case, a computer simulation based upon elementary quantum processes occurring in the laser radiation field is presented. Using this method, the electron multiplication coefficient in the discharge is calculated for several values of laser quanta energies. In the case of large laser quanta, the multiplication coefficient in argon is found to be higher than is predicted by the classical theory. It is shown that helium, not having a Ramsauer minimum, does not reveal a similar feature. Comparing our theoretical results with those of experiments from the literature, information is obtained on the role photoionization from upper excited levels of argon plays in the breakdown process.