Survival of Metastable Hydrogen Atoms Passing Through Crossed Electric and Magnetic Fields

Abstract

In the present experiment, the motional electric field responsible for the quenching (and polarization) of metastable hydrogen atoms passing through a magnetic field, is compensated, for a prescribed atomic velocity, by a static electric field. The resulting continuous velocity selection has been tested over a wide range of velocities ((5 ÷ 40) km/s). The relative velocity dispersion ranges from 5% at 40 km/s, to 22% at 5 km/s. As is confirmed by a calculation, the resolution is mainly determined by the quality of the matching of the two field profiles.

Maxwell Duality, Lorentz Invariance, and Topological Phase

“…Such motional Stark shifts have already been seen experimentally, but have not hitherto been interpreted in terms of the HMW phase [15][16][17]. We also propose a different direct HMW phase measurement using a Ramsey two-pulse interferometer with ammonia beams and microwaves [20].…”

“…It is a previously measured effect that has been seen with both applied external electric fields [14] and with magnetic-induced motional Röntgen electric fields [15,16,18]. In the latter case, the effect was used as a magnetic-field dependent beam polarizer in 1952 by Lamb and Retherford [15] and more recently by Robert, et al, as a velocity selector [16]. The earliest observation of motional Stark quenching was probably made in 1916 by Wien [18].…”

“…This electric-field-induced decay is called the "Stark quenching" of metastable, hydrogen-like atoms. It is a previously measured effect that has been seen with both applied external electric fields [14] and with magnetic-induced motional Röntgen electric fields [15,16,18]. In the latter case, the effect was used as a magnetic-field dependent beam polarizer in 1952 by Lamb and Retherford [15] and more recently by Robert, et al, as a velocity selector [16].…”

“…Suppose we have a source of metastable hydrogen atoms in the 2s state (Fig. 2), which are easily made [13][14][15][16]18]. Such atoms have an exceedingly long lifetime of about τ 2s = 0.14 s, since the transition to the ground state is dipole forbidden [17].…”

Collisions at thermal energy between metastable hydrogen atoms and hydrogen molecules: total and differential cross sections

“…An analysis of these different contributions would require monokinetic H* and H2 beams, plus an analysis of the final H* velocity• This can be done, in principle, by using a nozzle beam of H2, and a continuous velocity selection of H* atoms by means of crossed electric and magnetic fields [14]. Nevertheless, the elastic process and the 2s-2p interconversion process are expected to dominate at small angles [15].…”