Attosecond Noncollinear Four Wave Mixing

Attosecond pulses produced by high harmonic generation are excellent sources of broadband excitation in the extreme ultraviolet. Such pulses can be used to produce coherent superpositions of electronic and vibrational states in atoms and small molecules. The resultant coherent superpositions, or wave packets, can then probed by a time-delayed optical pulse, which modifies the polarization of the medium by coupling to neighboring states. The time dependent spectral interferences in this method, called attosecond transient absorption in the collinear configuration, are recorded with outstanding temporal and spectral resolution to reveal electronic and vibrational structure and dynamics.