Observation of Quantum Effects in sub Kelvin Cold Reactions

TL;DR

This paper reports the first experimental observation of quantum effects in cold chemical reactions at temperatures as low as 10 millikelvin, using merged neutral supersonic beams to achieve low collisional velocities.

Contribution

It introduces a novel experimental method with merged neutral beams to observe quantum effects in chemical reactions at ultra-low temperatures.

Findings

Observation of orbiting resonances in Penning ionization reactions.

Reaction rate sharply increases at temperatures around a few kelvin down to 10 mK.

Method applicable to various canonical chemical reactions.

Abstract

There has been a long-standing quest to observe chemical reactions at low temperatures where reaction rates and pathways are governed by quantum mechanical effects. So far this field of Quantum Chemistry has been dominated by theory. The difficulty has been to realize in the laboratory low enough collisional velocities between neutral reactants, so that the quantum wave nature could be observed. We report here the first realization of merged neutral supersonic beams, and the observation of clear quantum effects in the resulting reactions. We observe orbiting resonances in the Penning ionization reaction of argon and molecular hydrogen with metastable helium leading to a sharp increase in the absolute reaction rate in the energy range corresponding to a few degrees kelvin down to 10 mK. Our method is widely applicable to many canonical chemical reactions, and will enable a breakthrough in the experimental study of Quantum Chemistry.