Wavepacket diagnosis with chirped probe pulses

For linearly chirped probe pulses, the observable pump-probe signal can be obtained analytically under useful idealizations: Gaussian packet and pulse, linear chirp, linear difference potential, and constant wavepacket group velocity within the probe window. These conditions allow the expression of the signal as a cross correlation between packet and probe window traveling in coordinate space at velocities upsilon and upsilon(1), respectively. The signal delay and its integrated area are independent of chirp. Relative to zero-chirp, the signal is temporally compressed for 0 < upsilon/upsilon(1) < 2, and becomes a minimum when packet and window co-propagate, upsilon = upsilon(1). Experimental data are used to illustrate wavepacket diagnosis in a real system. (C) 1998 Elsevier Science B.V. All rights reserved.