Effects of vibrational and rotational excitation on the decay of cold trapped Rydberg NO molecules

The large static electric dipole moments of molecules in high Rydberg states allows efficient deceleration and trapping using inhomogeneous electric fields [1]. This has enabled, e.g., studies of slow Rydberg state decay processes [2], and ion-molecule reactions at temperatures <100 mK [3]. Here we describe the use of a cryogenically-cooled chip-based Rydberg-Stark decelerator, to electrostatically trap nitric oxide (NO) molecules in long-lived Rydberg states for up to 5 ms [4,5]. Trap decay rates were measured for molecules in Rydberg states with principal quantum numbers, n, between 32 and 50, in series converging to the N⁺ = 0 - 6 rotational states of the v⁺ = 0, and 1 vibrational states of NO⁺. For a given value of N⁺, similar decay time constants were measured for both vibrational series. However, these decay time constants do not follow the typical n-scaling of atomic Rydberg states. Instead they generally decrease as the value of n increases. This observation is attributed to the effects of vibrational channel interactions with short lived (~ 1 ps) low-n vibrationally excited states that lie close to v⁺ = 0 and 1 series limits. Furthermore, as N⁺ was increased the measured decay time constants decreased, because of the combined effects of an increased density of states and inherent predissociation. States in low-N⁺ series are of interest for ion-molecule reactions studies, with states in high-N⁺ series being important for trace gas sensing [6].

[1] S. D. Hogan, EPJ Techniques and Instrumentation 3, 1 (2016)

[2] S. D. Hogan, Ch. Seiler, F. Merkt, Phys. Rev. Lett. 103, 123001 (2009)

[3] K. Höveler, J. Deiglmayr, J. A. Agner, R. Hahn, V. Zhelyazkova, F. Merkt, Phys. Rev. A 106, 052806 (2022)

[4] A. Deller, M. H. Rayment, S. D. Hogan, Phys. Rev. Lett. 125, 073201 (2020)

[5] M. H. Rayment, and S. D. Hogan, Phys. Chem. Chem. Phys. 23, 18806 (2021)

[6] J. Schmidt, M. Fiedler, R. Albrecht, D. Djekic, P. Schalberger, H. Baur, R. Löw, N. Fruehauf, T. Pfau, J. Anders, E. R. Grant, H. Kübler, Appl. Phys. Lett. 113, 011113 (2018)