Alignment enhanced spectra of molecules in intense non-resonant laser fields

The dipole moment induced in a polarizable molecule by an intense non-resonant laser field interacts with the field to create aligned pendular states of definite parity, hybrids of the field-free rotational states. Electric dipole transitions between these states, driven either by a permanent moment (if the molecule is polar) or the induced moment (whether polar or non-polar), give rise to characteristic spectral features. For perpendicular transitions, at high fields the librational period of the molecular axis becomes directly observable. For parallel transitions in Raman spectra, the axis alignment can markedly enhance the transition probability by ≈ 103 or more.