Radiation pressure force from optical cycling on a polyatomic molecule

Abstract

We demonstrate multiple photon cycling and radiative force deflection on the triatomic free radical strontium monohydroxide (SrOH). Optical cycling is achieved on SrOH in a cryogenic buffer-gas beam by employing the rotationally closed P (N = 1) branch of the vibronic transitionX 2 Σ + (000) ↔Ã 2 Π 1/2 (000). A single repumping laser excites the Sr-O stretching vibrational mode, and photon cycling of the molecule deflects the SrOH beam by an angle of 0.2 • via scattering of ∼ 100 photons per molecule. This approach can be used for direct laser cooling of SrOH and more complex, isoelectronic species.

Cold collisions of heavy Σ2 molecules with alkali-metal atoms in a magnetic field: Ab initio analysis and prospects for sympathetic cooling of SrOH(Morita1, Kłos2, Buchachenko3 et al. 2017Phys. Rev. A252441View full textAdd to dashboardCite

“…We find that inelastic spin relaxation in fully spin-polarized Li + SrOH collisions is strongly suppressed (with the ratio of elastic to inelastic collision rates γ > 10 2 -10 3 ), suggesting good prospects for sympathetic cooling of spin-polarized SrOH molecules with Li atoms in a magnetic trap. In the context of rapid experimental progress in buffer-gas cooling and Sisyphus laser cooling of polyatomic radicals [20,35,36], our results open up the possibility of sympathetic cooling of polyatomic molecules with magnetically co-trapped ultracold alkali-metal atoms, potentially leading to new advances in low-temperature chemical dynamics and spectroscopy of large molecules in the gas phase [30,37].…”

“…Cooling and trapping polyatomic molecular radicals is expected to provide new insights into many-mode vibrational dynamics, photochemistry, and chemical reactivity at ultralow temperatures [20,[30][31][32][35][36][37] [20,36].…”

Coherent Bichromatic Force Deflection of Molecules

“…SrOH has 12 ground state sublevels coupled to 4 excited states, yet we achieve F BCF ≈ 1.1 kγ/2 which is effectively the size of the radiative force on an ideal two-level system. This can be compared with other radiative force experiments on diatomic [52] and polyatomic molecules [46], which have previously shown F rad ≈ kγ/7 and kγ/4, correspondingly. Thus, large resonant optical forces on molecules are possible with the use of coherent bichromatic optical fields to induce stimulated forces.…”

A Diatomic Molecule is One Atom too Few

“…Recently, following initial theoretical proposals [35,36] and proof-of-principle experimental results [37], laser cooling has been achieved for SrF [38], YO [39], and CaF [40,41], including a magnetooptical trap (MOT) for SrF [42][43][44]. Motivated by this progress on diatomic molecules, and building upon previous theoretical work [45], we recently demonstrated photon cycling-a crucial requirement for achieving light induced forces-with the triatomic molecule SrOH [46]. However, since SrOH had 3 distinct vibrational modes, including a doubly degenerate bending mode, and because Doppler cooling required scattering an order of magnitude more photons as compared to deflection experiments, the question of direct laser cooling remained open.…”