Association of molecules using a resonantly modulated magnetic field

TL;DR

This paper investigates how resonant magnetic field modulation can optimize molecule formation from atomic gases, analyzing the effects of amplitude, frequency, temperature, and mean-field interactions on conversion efficiency.

Contribution

It introduces a detailed model of magnetic field modulation for molecule association, highlighting optimal parameters and the influence of temperature and mean-field effects.

Findings

Maximal conversion achieved by optimizing amplitude and frequency.

Resonant coupling depends on atomic pair energy and modulation parameters.

Higher temperatures broaden the resonance, reducing frequency dependence.

Abstract

We study the process of associating molecules from atomic gases using a magnetic field modulation that is resonant with the molecular binding energy. We show that maximal conversion is obtained by optimising the amplitude and frequency of the modulation for the particular temperature and density of the gas. For small modulation amplitudes, resonant coupling of an unbound atom pair to a molecule occurs at a modulation frequency corresponding to the sum of the molecular binding energy and the relative kinetic energy of the atom pair. An atom pair with an off-resonant energy has a probability of association which oscillates with a frequency and time-varying amplitude which are primarily dependent on its detuning. Increasing the amplitude of the modulation tends to result in less energetic atom pairs being resonantly coupled to the molecular state, and also alters the dynamics of the transfer from continuum states with off-resonant energies. This leads to maxima and minima in the total conversion from the gas as a function of the modulation amplitude. Increasing the temperature of the gas leads to an increase in the modulation frequency providing the best fit to the thermal distribution, and weakens the resonant frequency dependence of the conversion. Mean-field effects can alter the optimal modulation frequency and lead to the excitation of higher modes. Our simulations predict that resonant association can be effective for binding energies of order $h \times 1$ MHz.