Knowledge Bank

Fluorescence spectroscopy, following two-photon excitation of Rydberg levels in molecular sodium, has been performed. Several methods are introduced and used to identify those two-photon transitions and analyzed the spectra. Using these methods, the rotational quantum number, energy and electronics character of the upper level may be determined without any assumptions about the state to which the upper level belongs. Twenty-nine two-photon transitions were observed. Most of them were associated with the $\mathrm{<mrow\; data-mjx-texclass="ORD">1</mrow>}\Sigma +g$ (3S-5S) state and used to calculate new values of the Dunham coefficients for that state. These were in close agreement with values obtained in polarization labeling experiments.$\mathrm{<mrow\; data-mjx-texclass="ORD">1</mrow>}$