QUANTUM-THEORY OF RESONANT SCATTERING OF ATOMS BY A PULSED-FIELD UNDER COHERENT POPULATION TRAPPING CONDITIONS

We develop an entirely quantum mechanical analytical description of sc attering of atoms with angular momenta j(g)-->j-->j(e)=j (j is an inte ger)by a pulsed sigma(+)-sigma(-) field. In the stationary-atom approx imation with exact accounting for recoil effects, we solve the problem of the change in the distribution of atoms among the internal and tra nslational degrees of freedom initiated by a single pulse for j(g) = 1 , 2. We find in analytical form recurrence formulas that make it possi ble to calculate the distribution of the atoms after an arbitrary sequ ence of pulses has acted on the system. We show that for discrete (res onant) values of the time interval between the pulses, the action of N pulses leads to effective formation and narrowing of peaks at discret e points in momentum space and to a broadening of the envelope of thes e peaks. In the case of a broad initial momentum distribution we deriv e explicit formulas for the peaks and the envelope and study their asy mptotic behavior for N much greater than 1. Finally, in the weak-field limit we study numerically the dependence of the contrast of the scat tering diagram on pulse length. (C) 1998 American Institute of Physics .