Determination of the spin-rotation fine structure of He2+

Jansen, Paul

Permalink

https://hdl.handle.net/2142/100567 Copy

Description

Title

Determination of the spin-rotation fine structure of He2+

Author(s)

Jansen, Paul

Contributor(s)

• Merkt, Frederic
• Semeria, Luca

Issue Date

2018-06-21

Keyword(s)

Cold and ultracold molecules

Abstract

Measuring spin-rotation intervals in molecular cations is challenging, particularly so when the ions do not have electric-dipole-allowed rovibrational transitions. We present a method to determine the spin-rotational fine structure of molecular ions from the fine structure of high Rydberg statesa . The method is illustrated by the determination of the so far unknown spin-rotation fine structure of the fundamentally important He2 + ion in the X+ 2Σ + u ground electronic state. The interaction that is responsible for the level structure in the high Rydberg states of He2 that were probed in our experiment is the n-independent spin-rotation interaction of the ion core. As a consequence, the fine-structure splittings in He2 + can be related to the fine-structure of the Rydberg states by applying an angular-momentum basis transformation from Hund’s case (e[b]) to Hund’s case (d). The experiment relies on the use of single-mode cw radiation to record spectra of high Rydberg states of He2 from the a 3Σ + u metastable state. Metastable helium molecules are produced by striking a discharge in a pulsed expansion of neat helium gasb . Cooling the valve body to a temperature of 10 K and using continuous-wave excitation results in an observed Doppler-limited linewidth of 25 MHz. The fine structure of Rydberg states of He2 is determined from strict selection rules by comparing the observed splitting of the Rydberg spectrum with the spin-rotational intervals of the initial metastable state. The fine-structure splittings of the v + = 0, N + = 1, 3, and 5 levels of He2 + are 7.96(14)MHz, 17.91(32) MHz and 28.0(6) MHz, respectively.

Publisher

International Symposium on Molecular Spectroscopy

Type of Resource

text

Language

eng

Permalink

http://hdl.handle.net/2142/100567

DOI

10.15278/isms.2018.RG07

Copyright and License Information

Copyright 2018 Paul Jansen

Owning Collections