Spectrum of Field-Ionized Triplet Gerade Rydberg States of H 2 and Comparison to Multichannel Quantum-Defect Theory

• Published in: The journal of physical chemistry. A, Molecules, spectroscopy, kinetics, environment, & general theory Molecules, spectroscopy, kinetics, environment, & general theory, 2019-04, Vol.123 (16), p.3535-3542
• Main Authors: Setzer, William J, de Magalhaes, Alexander, Morgan, Thomas J
• Format: Article
• Language: English
• ISSN: 1089-5639; 1520-5215
• DOI: 10.1021/acs.jpca.9b01445

A spectrum of field-ionized triplet Rydberg states of gerade symmetry H2 has been measured, excited from the v''=0, N''=1-3 rovibrational levels of the metastable c3Πu-, 2pπ state in a 6 keV fast molecular beam. The field-ionized spectrum is kinetic energy labeled in order to separate it from the well-studied v+ ≥ 1 autoionization spectrum. The spectrum consists of both ns and nd Rydberg series with n between 10 and 28 converging to the v+=0, N+= 1-3 levels of the X+ 2Σg+ ground state of H2. Transitions with changes in vibration and/or rotation are also identified. The spectral positions of 59 transitions in the field ionization spectrum are identified and assigned quantum numbers using the predictions of multichannel quantum-defect theory (MQDT). The transition energies and subsequent effective quantum defects are compared between experiment and theory. Most of the observed transitions, within the experimental uncertainty of 0.2 cm-1, agree with the energies predicted by MQDT.