Coherent dynamics of multilevel systems

In this paper we report the results of an experimental study of the coherent dynamics (CD) of the (2J + 1), with J = 1, 2⋯6, low-field, equally spaced Zeeman components of the oxygen molecule Of (O ¹⁶-O¹⁶) and O₂³⁴ (O ¹⁶-O¹⁸) driven by a radio frequency (rf) field in a supersonic molecular beam. A supersonic molecular beam magnetic resonance spectrometer has been employed in the "flop out" mode, where two intense inhomogeneous magnetic fields are antiparallel, so that the resonating Zeeman levels are defocused at the detector, diminishing the beam intensity. The experimental signal interrogates the total number of molecules in a given total angular momentum state J which changed their initial M_J component. The rf amplitude spectroscopy has been applied to study the dependence of the signal on the amplitude of the rf field for various Zeeman manifolds on-resonance, and to investigate the dependence of the signal on the rf frequency. An analytical solution for the coherent dynamics of a spin J system driven by an rf field, which is valid both for on-resonance and for off-resonance situations, was utilized for the analysis of the experimental data. This confrontation between experiment and theory elucidated some of the universal features of the CD of multilevel systems. Inhomogeneous dephasing of the CD effects, which is due to the velocity distribution in the beam, was quantitatively analyzed, providing a novel method for the determination of translational temperatures in supersonic beams.