Knowledge Bank

In this contribution, we analyze the rotationally resolved spectra for two-photon excitation of NO $(X2\Pi ,v)$ to its Rydberg States: $C2\Pi ,D2\Sigma ,F2\Delta$ and $H2\Pi ,2\Sigma$. The spectra are analyzed in terms of the non-vanishing components of the two-photon absorption spherical tensor operator. In this way, a minimum number of parameters is sufficient to model the rotational as well as the polarization dependence of the two-photon linestrength: a prerequisite for the state specific detection of rotational alignment in product ensembles resulting from different collision or photodissociation processes. In addition, perturbations between different electronic state$s¯$ (homogenous, e. g. C.$B2\Pi$ or heterogenous, e.g. $H2\Pi ,2\Sigma$) are incoporated in a straight forward way using for example, an expansion in terms of Hund’s case a) basis functions. (2+1) resonance enhanced multiphoton ionization spectra are recorded under molecular beam and various free jet expansion conditions covering a temperature range from 2K to 300K. Higher rotational and vibrational states are accessed via the photodissociation of $NO2$ in a (single color) laser molecular beam experiment.