Probing weakly bound long-range Rydberg molecules by quantum beating experiments in rubidium vapor
Weakly bound long-range Rydberg molecules (LRRM) associated with rubidium atomic states with low angular momentum and very low principal quantum numbers (7$s$, 8$s$, 5$d$, 6$d$) are observed in a quantum beating experiment for the first time. The experiments are conducted using parametric four-wave mixing (PFWM) in a pump-probe fashion. Fourier analysis of the time-domain data yields a spectrum on which various quantum beats are identified. Energy spacings between adjacent vibrational levels within each LRRM's quantum well manifest on the spectrum as overtones on both sides of the 7$s$-5$d_{5/2}$ and 8$s$-6$d_{5/2}$ atomic quantum beats at 18.225 THz and 10.726 THz, respectively. From the observed vibrational term energy spacings, we are able to extract vibrational constants for three potential wells and calculate their dissociation energies and potential energy curves using Morse potential. Despite the fact that there are no direct results published in the literature associated with $s$ and $d$ states at our principal quantum numbers, we are able to validate our observations by comparing our vibrational constants with those of the $p$ state and our dissociation energies with those extrapolated from higher principal quantum numbers. The comparison shows excellent agreement with existing studies. The study demonstrates a new experimental technique to study LRRM that does not involve Bose-Einstein condensates and yet can resolve vibrational levels within quantum wells of several cm$^{-1}$ deep. The technique is also versatile in studying heteronuclear and polyatomic LRRM.
quantum beating, quantum beat, quantum beat spectroscopy, spectroscopy, laser spectroscopy, rubidium, long-range molecules, long-range Rydberg molecules, Rydberg molecules
University of Illinois - Urbana-Champaign
Networked Digital Library of Theses and Dissertations
University of Illinois at Urbana-Champaign