Photodissociation of ultracold diatomic strontium molecules with quantum state control

TL;DR

This study demonstrates precise quantum control over ultracold diatomic strontium molecules during photodissociation, revealing quantum effects like tunneling and interference, and challenging classical models with a fully quantum mechanical description.

Contribution

It achieves complete quantum state control of the continuum in ultracold molecules using photodissociation, enabling new insights into ultracold chemistry and quantum dynamics.

Findings

Observation of resonant and nonresonant barrier tunneling

Detection of matter-wave interference of reaction products

Identification of forbidden reaction pathways

Abstract

Chemical reactions at ultracold temperatures are expected to be dominated by quantum mechanical effects. Although progress towards ultracold chemistry has been made through atomic photoassociation, Feshbach resonances and bimolecular collisions, these approaches have been limited by imperfect quantum state selectivity. In particular, attaining complete control of the ground or excited continuum quantum states has remained a challenge. Here we achieve this control using photodissociation, an approach that encodes a wealth of information in the angular distribution of outgoing fragments. By photodissociating ultracold 88Sr2 molecules with full control of the low-energy continuum, we access the quantum regime of ultracold chemistry, observing resonant and nonresonant barrier tunneling, matter-wave interference of reaction products and forbidden reaction pathways. Our results illustrate the failure of the traditional quasiclassical model of photodissociation and instead are accurately described by a quantum mechanical model. The experimental ability to produce well-defined quantum continuum states at low energies will enable high-precision studies of long-range molecular potentials for which accurate quantum chemistry models are unavailable, and may serve as a source of entangled states and coherent matter waves for a wide range of experiments in quantum optics.