Ultranarrow extraresonant antiholes in pump–probe spectroscopy induced by inelastic collisions

Abstract
Pump–probe spectroscopy with copropagating pump and probe beams of an open two-level system where, as a result of inelastic collisions, the lower state of an optical transition relaxes faster to reservoir states than the upper state does, may yield an antihole in the probe spectral profile whose linewidth is subnatural and unaffected by Doppler broadening.