Cold ion chemistry within Coulomb crystals

Abstract

Coulomb crystals are ordered structures of spatially-localised ions, held within an ion trap and exhibiting very low translational temperatures. The many advantages of studying the spectroscopic, kinetic and dynamic properties of gas phase ions in Coulomb crystals -such as the ability to manipulate and detect single ions under ultrahigh vacuum conditions -have seen their adoption in an ever-expanding range of fields. This article provides an overview of recent developments, where Coulomb crystals have been utilised for precision measurements, for the study of controlled ion-neutral reactions and in the implementation of quantum information science. ARTICLE HISTORY

Vibrational overtone spectroscopy of cold trapped hydroxyl anions

“…Our group has performed rotational spectroscopy on the triatomic anion NH 2 − [12] precluding the tentative assignment that this species supports an interstellar absorption feature. The sensitivity in ion-molecule studies within Coulomb crystals has also allowed for the testing of non-Langevin behavior at ultracold temperatures [13]. In proton-transfer between sympathetically cooled N 2 H + and rotationally cold H 2 O, nuclear spin isomer-dependent reaction rates were reported [14].…”

Strong inverse kinetic isotope effect observed in ammonia charge exchange reactions

“…The Xe þ ions are allowed to react (charge transfer) with a thermal sample of ammonia gas, and reactions are monitored by (indirectly) observing the appearance of ammonia ions. The many advantages of using Coulomb crystals for the study of reaction processes, and the details of the ion trap system used in this work, have been described elsewhere [13][14][15][16][17][18][19][20][21][22][23] . Combining laser-induced fluorescence images with time-of-flight (ToF) mass spectrometry (MS) allows for the quantitative calculation of reaction rate constants for the systems of interest, namely Xe þ ( 2 P 3=2 ) + NH 3 ( 1 A 1 ) and Xe þ ( 2 P 3=2 ) + ND 3 ( 1 A 1 ) (see Fig.…”

A simple experimental system to illustrate the nonlinear properties of a linear chain under compression

“…The buckling of a linear chain has also been found relevant to mechanical properties of engineered materials 20 and to active colloidal chains in biology 21 . As mentioned, buckled structures commonly occur in formations of cooled ions in traps; these in turn find a range of advanced applications in spectroscopy, quantum computing and reaction kinematics (see 22 for a recent review).…”