FEATURES OF THE TIME SHAPE OF THE PRESSURE PULSES OF OPTICAL AIR BREAKDOWNA. N. Chumakov,a A. M. Petrenko,b and N. A. Bosaka UDC 534.222.2:621.373 The time shape and amplitude of pressure pulses initiated by surface laser air breakdown for different energies of laser pulses (1-180 mJ) has been compared to the results of numerical gasdynamic calculations of unsteady explosive motions with allowance for counterpressure at distances of 0.2 to 30 cm from the breakdown region. It has been established that the experimental pressure pulse has the character of slowly damped quasiperiodic vibrations, whereas the calculated pulse is a bipolar single pulse of a much shorter duration. Good agreement between the experimental and calculated amplitudes of a positive pressure phase has been found throughout the investigated range, whereas the agreement between the corresponding amplitudes and durations of a negative pressure phase is limited in character. The differences observed in the experimental and calculated data have been attributed to the transformation of the shock-wave motion to acoustic radiation. aInstitute of Molecular and Atomic Physics, National Academy of Sciences of Belarus, Minsk, Belarus; bInstitute of Solid and Semiconductor Physics, National Academy of Sciences of Belarus, Minsk, Belarus. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 76, No. 4, pp. 89-94, July-August, 2003. Original article submitted November 26, 2002.