CPMMW spectroscopy of rydberg states of nitric oxide

Abstract

The spectroscopy of Rydberg states of NO has a long history [1], stimulating both experimental and theoretical advances in our understanding of Rydberg structure and dynamics. The closed-shell ion-core ($^{1}$$\Sigma$$^{+}$) and small NO$^{+}$ dipole moment result in regular patterns of Rydberg series in the Hund’s case (d) limit, which are well-described by long-range electrostatic models (e.g., [2]). We will present preliminary data on the core-nonpenetrating Rydberg states of NO (orbital angular momentum, $\ell$ $\geq$ 3) collected by chirped-pulse millimeter-wave (CPmmW) spectroscopy. Our technique directly detects electronic free induction decay (FID) between Rydberg states with $\Delta$n $\approx$ 1 in the region of n $\sim$ 40-50, providing a large quantity (12 GHz bandwidth in a single shot) of high quality (resolution $\sim$ 350 kHz) spectra. Transitions between high-$\ell$, core-nonpenetrating Rydberg states act as reporters on the subtle details of the ion-core electric structure. $\\$ $\\$ [1] Huber KP. Die Rydberg-Serien im Absorptions-spektrum des NO-Molek$\ddot{\text{u}}$ls. $Helv.$ $Phys.$ $Acta$ $\bf{3}$, 929 (1961). $\\$ $\\$ [2] Biernacki DT, Colson SD, Eyler EE. Rotationally resolved double resonance spectra of NO Rydberg states near the first ionization limit. $J.$ $Chem.$ $Phys.$ $\bf{88}$, 2099 (1988).