Separation of long-range and short-range interactions in Rydberg states of diatomic molecules

Abstract

Observation and analysis of the f([script-l]=3), g([script-l]=4), and h([script-l]=5) Rydberg series of CaF in the range 13<or=n<or=17 is presented. Simultaneous analysis of the f, g, and h Rydberg series of CaF, combined with significant improvements to the long-range model for nonpenetrating Rydberg states, provides a generally applicable scheme for separating the effects of the long-range (electric multipole and polarization) and short-range (core penetration) interactions between the Rydberg electron and ion core in diatomic molecules. Techniques for rigorous assignment of nonpenetrating states, as well as extensions of the long-range model, are discussed. Explicit formulas for the first- and second-order matrix elements of the first four anisotropic electric multipole interactions (electric dipole, quadrupole, octupole, and hexadecapole) are given. The discrepancies between the observed behavior and that predicted by the long-range model, which are particularly significant for the f series, are shown to be due to penetration of the Rydberg electron wavefunction within the ion core. We show that these penetration effects can be understood within the framework of ligand field theory and conclude with a discussion of the relative contributions of the long- and short-range interactions to the quantum defects of the core-penetrating "s," "p," and "d" series of CaF.

Broadband velocity modulation spectroscopy of ThF+ for use in a measurement of the electron electric dipole moment

“…The ThF dissociation energy is greater than the ionization energy [17,32], which may allow for greater flexibility in highly-efficient ion creation. One prospect is to prepare the neutral molecule in a core nonpenetrating high-l Rydberg state, where it can vibrationally autoionize without perturbing the ion core [42,43,44]. Additionally, resonance-enhanced multiphoton dissociation (REMPD) spectroscopy will be performed on ThF + .…”

Direct detection of Rydberg–Rydberg millimeter-wave transitions in a buffer gas cooled molecular beam

“…[1][2][3][4][5][6] Microwave and millimeter-wave spectroscopies capture Rydberg-Rydberg transitions with high resolution, sensitivity, and completeness. [7][8][9][10][11][12].…”

The Stark effect in Rydberg states of a highly polar diatomic molecule: CaF

“…5 A complementary extended long-range model, which included the 3 ഛ ᐉ ഛ 5, v + = 1 states from the region of 13ഛ n * ഛ 17, yielded the values for dipole and quadrupole moments and the isotropic polarizability. 6 The interaction among g͑−4͒, f͑−3͒, and d 2 ⌺ + states ͓here we use Hund's case ͑d͒ notation for the first two states: ᐉ͑ᐉ R ͒, where ᐉ R = N − N + is the projection of ᐉ on the ion-core rotational axis͔, as uncovered in the analysis of the lowest-N rotational levels presented in this paper, bridges the two models since in neither of the two previous models are all three of these states ͓g͑−4͒, f͑−3͒, and d 2 ⌺ + ͔ present together. However, limitations in our fitting capabilities and the current dataset have prevented a global fit involving both sets of data.…”

“…We have exploited the extended long-range model 6 to provide a zerofield description of the core-nonpenetrating states. Based on observation of the lowest-N rotational states, we have determined the core-penetrating characters admixed into the f, g, and h states and, by comparing the experimentally observed Stark effect patterns to the calculated ones, we show that our extended long-range model is valid for higher-ᐉ states, which had not been explicitly fitted in our determination of the long-range parameters and which first appear in the spectrum only when the electric field is applied.…”