Excitation and characterization of long-lived hydrogenic Rydberg states of nitric oxide

Abstract

High Rydberg states of nitric oxide (NO) with principal quantum numbers between 40 and 100 and lifetimes in excess of 10 µs have been prepared by resonance enhanced two-color two-photon laser excitation from the X 2 Π 1/2 ground state through the A 2 Σ + intermediate state. Molecules in these long-lived Rydberg states were detected and characterized 126 µs after laser photoexcitation by state-selective pulsed electric field ionization. The laser excitation and electric field ionization data were combined to construct two-dimensional spectral maps. These maps were used to identify the rotational states of the NO + ion core to which the observed series of long-lived hydrogenic Rydberg states converge. The results presented pave the way for Rydberg-Stark deceleration and electrostatic trapping experiments with NO, which are expected to shed further light on the decay dynamics of these long-lived excited states, and are of interest for studies of ion-molecule reactions at low temperatures. arXiv:2005.00090v1 [physics.chem-ph] 30 Apr 2020

Quantum-state-dependent decay rates of electrostatically trapped Rydberg NO molecules

“…Low-n states in the v + = 1 series that are located close to the v + = 0, N + = 0 series limit are also shown. The energies of the levels in this figure were either measured in our experiments, 39 or calculated using the methods described in Section 3.1.…”

Slow Decay Processes of Electrostatically Trapped Rydberg NO Molecules

“…Here, by preparing long-lived hydrogenic Rydberg states, for which predissociation is not the dominant decay mechanism, by two-color two-photon excitation from the X 2 Π 1=2 ground state [53][54][55][56], we report Rydberg-Stark deceleration and electrostatic trapping of NO. NO is a chemically important radical that plays a role in atmospheric physics, combustion, and trace gas detection [57].…”

“…two-color two-photon excitation scheme driven by radiation from two pulsed dye lasers (FWHM spectral width 0.17 cm −1 ) [53][54][55][56]. The first P 11 ð3=2Þ transition occurred at υ 1 ¼ 44193.988 cm −1 .…”

“…Transitions from the A 2 Σ þ state to Rydberg states with nlðN þ Þ ¼ npð0Þ and nfð2Þ character, where 34 ≤ n ≲ 60, occurred for υ 2 ¼ 30 435-30 505 cm −1 . Intramolecular interactions and stray electric fields caused ∼1% of the excited molecules to evolve, close to the time of excitation, into long-lived l-mixed hydrogenic Rydberg-Stark states with jm l j ≳ 3 and static electric dipole moments between 0 and ∼10 000 D [56].…”

“…The distribution of Rydberg-Stark states with n ¼ 43 was described by a Gaussian function centered on the Stark state with zero static electric dipole moment as determined from the electric field ionization measurements reported in Ref. [56]. The reduction in the amplitude of the TOF signal as ja t j was increased is a consequence of the reduced phase-space acceptance under these conditions and the geometry of the in situ detection region [41].…”