Chemical reactions of conformationally selected 3-aminophenol molecules in a beam with Coulomb-crystallized Ca+ ions

Abstract

Many molecules exhibit multiple conformers that often easily interconvert under thermal conditions. Therefore, single conformations are difficult to isolate which renders the study of their distinct chemical reactivities challenging. We have recently reported a new experimental method for the characterization of conformerspecific effects in chemical reactions [Y. P. Chang et al., Science 342, 98 (2013)]. Different conformers are spatially separated using inhomogeneous electric fields and reacted with a Coulomb crystal of cold, spatially localized ions in a trap. As a first application, we studied reactions between the two conformers of 3-aminophenol and Ca + . We observed a twofold larger rate constant for the cis compared to the trans conformer which was rationalized in terms of the differences in the long-range ion-molecule interactions. The present article provides a detailed description of the new method and a full account of the experimental results as well as the accompanying theoretical calculations.

Design and characterization of a linear quadrupole ion trap for high-resolution Coulomb-crystal time-of-flight mass spectrometry

“…REMS works best on small Coulomb crystals consisting of one single atomic or molecular ion that is sympathetically cooled by one laser cooled ion enabling the distinction of isotopes that differ by only one atomic mass unit (u) [12,13]. However, for larger mixed-species Coulomb crystals the REMS spectra become complex due to Coulomb coupling [14] and an unambiguous mass assignment is not always possible [15,16].…”

“…The development of molecular-beam machines coupled to LQTs enables the study of highly controlled ion-molecule reaction dynamics by allowing to select specific velocities, quantum states and conformations of the neutral molecules [3,10,[15][16][17]. Ion-molecule reactions with large organic molecules can have several channels that lead to a multitude of product ion species.…”

“…In a recent experiment, we studied the conformer specific reaction rate constants of 3-aminophenol with Ca+ Coulomb crystals [15,16]. REMS was used to analyze the product ions, but an unambiguous assignment was not possible because two possible products differ by only 1 u.…”

Rotational dynamics of a diatomic molecular ion in a Paul trap

“…Laser-cooled or sympathetically cooled atomic and molecular ions have been in the spotlight in recent years, due to their great potential in the study and development of many fields, such as chemical reactions, [1][2][3][4][5][6] high-precision spectroscopy, [7][8][9] atomic optics, and in many other fast developing fields related to quantum information and quantum computing, where the manipulation of the internal states of these ions has become possible. [10][11][12][13][14][15] One of the most applied techniques to trap these cold ions is known as the Paul trap, using time-dependent radiofrequency electric fields.…”

A Dynamic Ion–Atom Hybrid Trap for High‐Resolution Cold‐Collision Studies

“…The present setup can readily be used for the measurement of the variation of pseudo-first-order reaction rates with the collision energy. The determination of absolute bimolecular rate constants, however, requires the accurate calibration of the Rb densities in the interaction region which is notoriously challenging for beam experiments [33]. Procedures for an accurate determination of the Rb densities in the beam are currently being developed and will be reported elsewhere.…”