Absorption and recurrence spectra of hydrogen in crossed electric and magnetic fields

Abstract

The absorption spectrum of the hydrogen atom in crossed electric and magnetic fields was measured. The magnetic field was set at 6.002 T, and the electric field was fixed at several values from 750 to 1000 V/cm. The observations require several different theoretical methods for their interpretation: (1) The spectrum is unscaled, the recurrences are weak, and their periods vary with energy over the interval of the observations. This observation caused us to develop a chirped Fourier transform method to extract closed orbits from the measured spectra. (2) The absorption spectrum consists of quasidiscrete peaks superposed on a smoothly rising continuum. To interpret this observation, a theoretical model of the continuum absorption is created, and we get results consistent with the measurements. (3) The experiments distinguish between prompt and delayed electrons, corresponding to lifetimes of the excited hydrogen atoms that are, respectively, less than or greater than about 100 ns. (4) At high energies, the measured absorption spectrum contains some regular quasidiscrete states. We use an Einstein-Brillouin-Keller quantization method to identify these as states that lie close to the plane perpendicular to the magnetic field.