THEORY OF RESONANT MULTIPHOTON POPULATION TRANSFER IN XENON

We present calculations of population transfer to excited states of xe non that shift into six-photon resonance during intense, sub-100-fs la ser pulses. If the excited-state lifetime is comparable to or longer t han the pulse width, the amount of population trapped in the excited s tate exhibits interference fringes as a function of peak intensity due to the double passage through resonance during the laser pulse. These interference fringes can reveal information about the behavior of exc ited states at intensities well above resonance, including stabilizati on against ionization. The population transfer can also be affected by using chirped pulses which make the passages through resonance asymme tric. A strong dependence on the sign of the chirp is found due to the finite lifetime of the excited state. We discuss prospects for observ ing this interference experimentally.