A theoretical study of delta-kick collimation (DKC) of heteronuclear Feshbach molecules is presented for condensed and thermal ensembles under various interaction regimes and temperatures. It is shown that DKC significantly reduces the expansion energy of the molecular cloud and beam divergence, achieving expansion energies on the order of picokelvins — a result comparable to the best experimental achievements for atoms. It is found that vibrational and translational degrees of freedom remain strongly decoupled, ensuring molecular stability during the pulse. These findings lay the groundwork for experiments with degenerate ground-state molecules, for straightforward pulsed molecular interferometry, and for precision measurements involving two species of particles, such as testing the universality of free fall.
A push at the right moment stops a swing. The delta-kick—a short laser pulse—was applied to a cloud of molecules, and it froze, like a swing after a precise kick. Molecules made of two different atoms, like a seat firmly locked to the swing’s bar, didn't fall apart during deceleration. The temperature dropped to picokelvins—trillionths of a degree above absolute zero, where motion nearly freezes and энтропия (a measure of disorder) becomes minimal. Even the internal jitter of atoms didn't disturb the stillness—like a passenger's slight swaying doesn't change the swing's motionlessness. An unexpected fact: at this temperature, the molecular cloud expands slower than grass grows. Now these nearly immobile objects are used to test the law of universal gravitation, which Галилей tested by dropping cannonballs from a tower, and Эйнштейн linked to кривизной пространства-времени. Based on them, scientists will build световую молекулярную интерферометрию—a device capable of detecting even the tiniest deviations.
🎯 At a temperature of one picokelvin, molecules move so slowly that crossing the width of a human hair would take them a full minute.