arXiv subjects

J. R. Bochinski

Publications and source records attributed to J. R. Bochinski.

5 recordsLinked to original sources

arXiv2005

Production of cold formaldehyde molecules for study and control of chemical reaction dynamics with hydroxyl radicals

We propose a method for controlling a class of low temperature chemical reactions. Specifically, we show the hydrogen abstraction channel in the reaction of formaldehyde (H$_{2}$CO) and the hydroxyl radical (OH) can be controlled through either the molecular state or an external electric field. We also outline experiments for investigating and demonstrating control over this important reaction. To this end, we report the first Stark deceleration of the H$_{2}$CO molecule. We have decelerated a molecular beam of H$_{2}$CO essentially to rest, producing cold molecule packets at a temperature of 100 mK with a few million molecules in the packet at a density of $\sim10^{6}$ cm$^{-3}$.

physics.atom-ph↗

arXiv2004

Efficient Stark deceleration of cold polar molecules

Stark deceleration has been utilized for slowing and trapping several species of neutral, ground-state polar molecules generated in a supersonic beam expansion. Due to the finite physical dimension of the electrode array and practical limitations of the applicable electric fields, only molecules within a specific range of velocities and positions can be efficiently slowed and trapped. These constraints result in a restricted phase space acceptance of the decelerator in directions both transverse and parallel to the molecular beam axis; hence, careful modeling is required for understanding and achieving efficient Stark decelerator operation. We present work on slowing of the hydroxyl radical (OH) elucidating the physics controlling the evolution of the molecular phase space packets both with experimental results and model calculations. From these results we deduce experimental conditions necessary for efficient operation of a Stark decelerator.

physics.atom-ph↗

arXiv2004

A pulsed, low-temperature beam of supersonically cooled free radical OH molecules

An improved system for creating a pulsed, low-temperature molecular beam of OH radicals has been developed. We use a pulsed discharge to create OH from H$_2$O seeded in Xe during a supersonic expansion, where the high-voltage pulse duration is significantly shorter than the width of the gas pulse. The pulsed discharge allows for control of the mean speed of the molecular packet as well as maintains a low temperature supersonic expansion. A hot filament is placed in the source chamber to initiate the discharge for shorter durations and at lower voltages, resulting in a translationally and rotationally colder packet of OH molecules.

physics.atom-ph↗

arXiv2004

Cold free radical molecules in the laboratory frame

A special class of molecules that are important to many subfields in molecular dynamics and chemical physics, namely free radical molecules, now enjoy a significant degree of center-of-mass motion control in the laboratory frame. The example reported in this paper concerns hydroxyl radical (OH), which, after the internal degrees of freedom are cooled in a supersonic expansion, has been bunched, accelerated, and slowed using time-varying inhomogeneous electric fields. In situ observations of laser-induced fluorescence along the beam propagation path allows for detailed characterization of the longitudinal phase-space manipulation of OH molecules by the electric fields. The creation of a pulse containing 1e3 to 1e6 molecules possessing a longitudinal velocity spread from 2 to 80 m/s around a mean laboratory velocity variable from 550 m/s to rest with only a few mm spatial extent represents an exciting and useful new experimental capability for exploring free radical dynamics. This paper offers the most detailed study of the Stark deceleration dynamics to date.

physics.atom-ph↗

arXiv2003

Phase Space Manipulation of Cold Free Radical OH Molecules

We report bunching, slowing, and acceleration of a supersonically cooled beam of diatomic hydroxyl radicals (OH). \textit{In situ} observation of laser-induced fluorescence along the beam propagation path allows for detailed characterization of longitudinal phase-space manipulation of OH molecules through the Stark effect by precisely sequenced inhomogeneous electric fields.

physics.atom-ph↗