Origin of elevated temperatures at large detuning

Determine the cause of the increased temperature observed in the single-beam narrow-line titanium magneto-optical trap at detunings greater than approximately 40 natural linewidths.

Background

The single-beam narrow-line magneto-optical trap exhibits a minimum vertical temperature near a detuning of approximately 30 natural linewidths. The temperature rises both near resonance and at larger detunings. The authors attribute the near-resonance increase potentially to off-resonant transitions that generate magnetic-force fluctuations, while the mechanism responsible for the increase at detunings above 40 linewidths is not established.

The paper proposes two possible explanations for the large-detuning heating: the finite diameter of the vertical cooling beam and the weaker radial magnetic forces at larger distances from the magnetic-trap center. These are presented as possibilities rather than a resolved explanation, leaving the physical origin of the observed temperature increase as an open question.

References

It is less clear why we also observe higher temperatures at large ($>40\,\gamma$) detuning; this temperature increase may be due to the finite beam diameter of the vertical beam and the weaker radial magnetic forces at large distance from the magnetic trap center.

— Narrow-line magneto-optical trap of titanium atoms  (2609.10725 - Duim et al., 9 Sep 2026) in Section 2.1, “Optimization of the single-beam MOT” (subsection labeled \ref{sec:vertical})