Multiorder rotational Raman transitions in molecular alignment and orientation

Nonresonant two-photon Raman transitions with ΔJ=±2 selection rules induce molecular alignment by altering the rotational quantum number J, whereas three-photon Raman transitions with ΔJ=±1 cause molecular orientation. Here, we perform a combined numerical and theoretical investigation to explore how these Raman transitions depend on laser intensity and to discern multiorder Raman transitions in laser-induced alignment and orientation going beyond two- and three-photon processes. Our results demonstrate the presence of higher-order transitions in molecular alignment and shed light on how alignment affects subsequent three-photon rotational Raman transitions as revealed by the alignment and orientation spectra and the Dyson series expansion of the unitary operator. As the laser pulse strength increases, multiorder transitions become directly observable, which can be utilized to enhance the alignment and orientation of molecules through the excitation of multiple rotational states.