Eur. Phys. J. D 26, 261-264 (2003)
https://doi.org/10.1140/epjd/e2003-00259-5

Molecular beam electric resonance without A- and B-fields

¹ Unidad de Láseres y Haces Moleculares, Instituto Pluridisciplinar, Universidad Complutense de Madrid, C/ Juan XXIII-1°, 28040-Madrid, Spain
² Fakultät für Physik der Universität Bielefeld, 4800 Bielefeld, Germany

Corresponding author: ^a laseres@pluri.ucm.es

Received: 9 May 2003
Published online: 12 August 2003

Abstract

We report on a novel phenomenon observed during the passage of a pulsed NO beam seeded in He through a combined homogeneous, static electric and RF field, denoted as C-field in a standard molecular beam electric resonance (MBER) experiment. Although we refrain from the state selective A- and B-fields, which are considered crucial for a MBER experiment, the transmitted intensity exhibits as a function of the RF frequency conspicuous dips at resonance frequencies that depend strictly linearly on the static field strength E₀. Their spectral width is by a factor of 4 smaller than the time of flight broadening. Both, the resonance frequencies and their linear field dependence can be precisely predicted applying a simple expression for the Stark effect to a transition of a single rotational state (J=3/2) of the electronic ground state . However, this formula is valid only in the high field limit ( kV/m) while the employed field ( kV/m) was in the extreme low field domain where the large Λ type doubling and hyperfine coupling lead to a purely quadratic Stark effect. We assume that the phenomenon is due to a yet unknown collective rather than to an isolated particle process.