Spectroscopy and dynamics of high orbital angular momentum Rydberg states

Abstract

Rydberg states of molecules with high orbital angular momentum (l >/~ 3) are a unique class of electronic states. These high-l Rydberg states escape the rapid non-radiative decay by predissociation, which is typical of the intensively studied low-4 Rydberg states. Access to high-4 Rydberg states is challenging due to the [delta]l = ±1 transition propensity rule in combination with the short lifetimes of the optically accessible, low- Rydberg states. To address these dual challenges, we implement optical-millimeter-wave stimulated Raman adiabatic passage (optical-mmW STIRAP), which enables efficient population transfer from a low-lying electronic state to a high-l Rydberg state without directly populating a lossy, low-e Rydberg state. Our demonstration of optical-mmW STIRAP on an atomic system includes examination of the experimental and theoretical details of every step of this coherent process and demonstrates its promise for molecular applications.

We explore the physics of the Rydberg electron <->ion-core system through investigation of the spectroscopy and dynamics of high-l Rydberg states of NO. We populate ng Rydberg states of NO by a three-color triple-resonance excitation scheme and probe Rydberg-Rydberg transitions by chirped-pulse millimeter-wave (CPmmW) spectroscopy. The precision of the experimental data obtained and the breadth of the state space examined by CPmmW spectroscopy provides challenges to the existing theory of the structure of high-l Rydberg states. We apply a long-range electrostatic model to disentangle and describe the physical mechanisms that contribute to the autoionization dynamics of NO Rydberg states. Our model accounts for the decay rates of vibrationally excited ng Rydberg states.

We explain the previously measured NO⁺ ion rotational state population distributions produced by autoionization of NO nf states and propose methods to generate single quantum state-selected NO⁺ ions by selective population of specific ng Rydberg states.