Producing Cold Molecules

N. Dam, Frans J. M. Harren, W. Leo Meerts +4 more

Břetislav Friedrich, John M. Doyle

Abstract Brrrr! Cold molecule and cold atom research are juxtaposed and the challenges in cooling and trapping molecules are recounted. Both indirect and direct techniques of producing cold and slow molecules (such as buffer‐gas cooling and magnetic trapping, see picture) are described. Advanced techniques of manipulating cold or slow molecules are reviewed and ongoing work with cold molecules is outlined. magnified image Herein, we aim to show why the work on translationally (and otherwise) cold molecules has sparked so much inspiration—and anticipation—in both the physics and chemistry communities. We begin by discussing the basic features of cold molecules as implied by their de Broglie wavelengths, large compared with molecular dimensions. We juxtapose cold molecule and cold atom research and recount the challenges that had to be met if molecules were to be cooled and trapped. Subsequently, both the indirect and direct techniques of producing cold and slow molecules are described in some detail, and their applicability to various classes of molecules is discussed. Advanced techniques of manipulating cold or slow molecules are illustrated by the examples of DC and AC trapping and storage. Finally, ongoing and future work with cold and/or trapped molecules is outlined. This includes precision spectroscopy, chemical reaction dynamics, simulations of few‐ and many‐body physics, quantum computing, and tests of fundamental physics.

Heather J. Lewandowski

Jason S. Alexander, Bryan J. Bichsel, Michael A. Morrison +2 more

Jeffrey J Kay, Sebastiaan Y. T. van de Meerakker, Kevin E. Strecker +1 more

We have produced translationally cold ammonia (ND3) molecules in various quantum states by kinematic cooling. In these experiments, ND3 molecules are brought nearly to rest in the (J, K) = (2,0), (2,1), (2,2), (3,1), (3,2), and (3,3) rotational levels of the ground vibronic state by rotationally-inelastic collisions with Ne atoms. The cold molecules are produced in quantum-state-dependent velocity distributions whose laboratory frame velocities are measured to be between 21 m s(-1) (E(trans)/k = 530 mk) and 32 m s(-1) (E(trans)/k = 1.2 K), and are calculated to be between 7.5 m s(-1) (E(trans)/k = 70 mK) and 27 m s(-1) (E(trans)/k = 880 mK). Due to systematic experimental effects, the measured velocities are upper limits to the actual velocities. These temperatures are low enough that it should be possible to use electrostatic traps to confine cold molecules in many of these quantum states.

Marin Pichler

Several different experiments involving the making of cold and ultracold molecules are performed and proposed. Ultracold cesium molecules are produced in a magneto-optical trap (MOT) by photoassociation near the 6P j, 7Pj, 9S 1/2, 6D3/2, 7D3/2 and doubly excited asymptotes. Perturbation effects related to resonant channel coupling were observed in photoassociation spectra below the 6 P1/2 asymptote. Such effects are used to illustrate a ground state ultracold molecule formation mechanism, which can also be formed in one step photoassociation to the double minimum 31S+m state. In addition, a new technique of making cold molecules of cesium hydride is proposed, using a cold hydrogen beam source and a cesium MOT. Due to reaction energetics, the formed CsH molecules should be in their lowest rovibrational states. ^