Cold and ultracold molecules in the twenties

Abstract

A diversity of experimental techniques has been developed over the last 25 years to create samples of molecular gases at temperatures close to the Absolute Zero—here we consider samples in the range from 10s of Kelvin (cold) down to 10s of nanoKelvin (ultracold). In these exotic physical environments, a range of novel experiments can be conducted which bring high levels of control over the properties of these ‘almost stationary’ molecules, in some cases with control over single trapped molecules achievable. In this article, recent advances in this field since 2020, both in terms of the ability to produce and manipulate the molecules and understand their properties, and also in the development of new applications of these technologies, are highlighted. Applications include observing explicit ‘quantum effects’ in chemical reactivity, developing an understanding of chemistry in cold astrophysical media, the creation of exotic phases of matter, the use of trapped molecules in quantum computation and simulations systems, and the use of very high-precision spectroscopic measurements to answer fundamental physics questions beyond the standard model of particle physics.

Quasi-integrability and nonlinear resonances in cold atoms under modulation

“…This is due to the rich internal structures, longer de Broglie wavelengths and tunable long-range interactions of ultracold atoms. Furthermore, the research in the regime of lower temperatures has also been extended to these molecules [ 51 , 52 ]. Apart from these recent developments, there has been a sustained effort to realize parallels between atomic and condensed matter physics [ 53 ].…”

Imaging Resonance Effects in C + H2 Collisions Using a Zeeman Decelerator

“…As the energy of these states and their effect on the scattering behavior are extraordinarily sensitive to the shape of the potential over the full range of interaction, the observation of these resonance effects can be considered one of the most stringent tests for theoretical models. Thus, there has been a continuous interest in performing controlled collision experiments at low energies. − …”

“…For example, the recently reported near-threshold VUV REMPI schemes for H/D or O­( 3 P ) atoms provide an interesting opportunity to investigate elementary reactive scattering processes, such as C + O 2 → CO + O ,, or complex-forming reactions between Zeeman-decelerated atoms and H 2 molecules. − A promising candidate is the S­( 1 D ) + H 2 → SH + H reaction, for which distinct resonance features have been predicted to occur at low energies in both ICSs and DCSs . Although a large body of work exists on these types of reactive systems, − ,,− there has been a continuous interest to study their scattering behavior under controlled and low-energy conditions − such as those provided by our combination of techniques.…”

“…Thus, there has been a continuous interest in performing controlled collision experiments at low energies. 26 − 31 …”

“… 61 − 63 A promising candidate is the S( 1 D ) + H 2 → SH + H reaction, for which distinct resonance features have been predicted to occur at low energies in both ICSs and DCSs. 64 Although a large body of work exists on these types of reactive systems, 7 − 9 , 63 , 65 − 67 there has been a continuous interest to study their scattering behavior under controlled and low-energy conditions 26 − 31 such as those provided by our combination of techniques.…”