Ultracold collisions of polyatomic molecules: CaOH

Abstract

Ultracold collisions of the polyatomic species CaOH are considered, in internal states where the collisions should be dominated by long-range dipole-dipole interactions. The computed rate constants suggest that evaporative cooling can be quite efficient for these species, provided they start at temperatures achievable by laser cooling. The rate constants are shown to become more favorable for evaporative cooling as the electric field increases. Moreover, long-range dimer states (CaOH) 2 * are predicated to occur, having lifetimes on the order of microseconds. which is exothermic by some 13 000 K. Ca(OH) 2 is a stable compound used in industrial applications like paper production and sewage treatment. It is not known whether the reaction (1) occurs at low temperatures in the gas phase. If it does, this is obviously a detriment to producing and maintaining a stable, ultracold gas of CaOH. We will disregard the possibility that the reaction occurs, both because the potential energy surface is unknown, and because, in the appropriate internal states, the molecules are expected to be shielded by the repulsive parts of the dipole-dipole interaction.This circumstance simplifies the description of scattering, and leads to certain common behaviors. In this article, exploiting the electric dipole moment of CaOH and considering a state that has a small parity doublet, we find that these behaviors still occur. The behaviors that we single out are: (1) a suppression of inelastic scattering at sufficiently high electric field and sufficiently low temperature, for states that can be optically trapped; and (2) a set of electric-field resonances, previously described as 'field linked states', [16,17] that could serve as an additional platform for controlling these species and their interaction.

1D Magneto-Optical Trap of Polyatomic Molecules

“…While diatomic molecules are a rich resource (and are only beginning to be explored), polyatomic molecules have qualitatively distinct advantages at the frontier of quantum science. Ultracold polyatomic molecules have been identified for applications including improved precision searches for the electron EDM [20] and for dark matter [21], novel quantum computation [22][23][24] and quantum simulation platforms [25,26], the control of the primordial chemical reactions that gave rise to life [27], the study of biomolecular chirality [28,29], and the study of ultracold collisions and quantum chemistry in increasingly complex systems, while maintaining single quantum state control [30,31].…”

Theoretical rovibronic spectroscopy of the calcium monohydroxide radical (CaOH)

“…6 The fields of ultracold molecules and precision tests of fundamental physics have been focusing on the alkaline earth monohydroxide radicals, notably CaOH. 7,8 The rovibronic energy level structure is particularly favourable when designing efficient laser cooling schemes and direct laser cooling of CaOH to temperatures near 1 mK has already been demonstrated in a one-dimensional magneto-optical trap. 9 Experimental schemes to extend cooling of CaOH into the microkelvin regime are actively being considered.…”

MARVEL analysis of the measured high-resolution rovibronic spectra of the calcium monohydroxide radical (CaOH)

“…We mention that the alkaline earth monohydroxide radicals, including CaOH (Kozyryev et al 2019;Augustovičová & Bohn 2019), are relevant in studies of ultracold molecules and precision tests of fundamental physics due to their favourable energy level structure. A list of highly accurate energy levels across multiple electronic states can be useful in this field, especially for the design of efficient laser cooling schemes which requires knowledge of molecular rovibronic structure to a high degree of accuracy.…”