Speaker
Michal Hejduk
Description
See the full Abstract at http://ocs.ciemat.es/EPS2018ABS/pdf/P4.4009.pdf
(Ultra)cold ion-neutral collisions for new (astro)chemistry
M. Hejduk1 , N. Coughlan1 , J. Toscano1 , L. Petralia1 , A. Tsikritea1 , J. Elworthy1 , H. McGhee1
T. P. Softley2 and B. R. Heazlewood1
1 PTCL, Department of Chemistry, University of Oxford, South Parks Road, Oxford OX1 3QZ,
United Kingdom
2 University of Birmingham, Edgbaston, Birmingham B15 2TT, United Kingdom
Our ultimate goal is to study low energy ion-neutral reactions on the threshold of the so
called “quantum regime”, i.e. under conditions when the de Broglie wavelength of the particles
is comparable to their dimensions. Furthermore, in order to reveal the full quantum nature of
the studied reactions, it is desirable to have the reactants in defined (electronic, ro-vibrational)
quantum states. Such demands on the reaction environment are not unnatural at all, as tempera-
tures in pre-stellar cores regularly reach approximately 10 K [1] and emission nebulae can reach
temperatures lower than 3 K of the microwave background radiation [2].
One way to achieve our objective is to store the ionic species in a cryogenic ion trap and
inject very slow neutral particles into it. As the temperature of the ions has to be very low
(a few Kelvin), they must be cooled sympathetically in a Coulomb crystal [3]. This would only
decrease their kinetic energy, though, so buffer gas cooling has to be employed as well. The
neutral reactants can be slowed down in Zeeman or Stark decelerators.
Exactly this kind of equipment is being developed in our group. Internal temperatures of
ionic species will reach < 10 K and the velocities of the neutral species will be as low as several
tens of metres per second. The reaction products, including those trapped in local minima of
potential energy surfaces, will be analysed by a time-of-flight mass spectrometer, by analysis
of the Coulomb crystal’s fluorescence image, and by action spectroscopy. To our knowledge,
this will be the first cryogenic Coulomb crystal device that incorporates neutral particle slowers
with these analytical methods.
Here we are going to present the current state of development and plans for the first measure-
ments.
References
[1] A. Roy, Ph. André, P. Palmeirim et al., Astronomy & Astrophysics 562, A138 (2004)
[2] R. Sahai and L. øA., The Astrophysical Journal Letters 487, L155 (1997)
[3] B. R. Heazlewood and T. P. Softley, Annual Review of Physical Chemistry 66, 475 (2015)
