Taming Molecular Collisions

The study of molecular collisions with the highest possible detail has been an important research theme in physical chemistry for decades. Over the last years we have developed methods to get improved control over molecules in a molecular beam [1]. With the Stark decelerator, a part of a molecular beam can be selected to produce bunches of molecules with a computer-controlled velocity and with longitudinal temperatures as low as a few mK. The molecular packets that emerge from the decelerator have small spatial and angular spreads, and have almost perfect quantum state purity. These tamed molecular beams allow for crossed beam scattering experiments with unprecedented levels of precision and sensitivity [2,3].

I will discuss our most recent results on the combination of Stark deceleration and velocity map imaging. The narrow velocity spread of Stark-decelerated beams results in scattering images with an unprecedented sharpness and angular resolution. This has facilitated the observation of diffraction oscillations in the state-to-state differential cross sections for collisions of NO with rare gas atoms [4,5].
References
[1] S.Y.T. van de Meerakker, H.L. Bethlem, G. Meijer, Nature Physics 4, 595 (2008).
[2] J.J. Gilijamse, S. Hoekstra, S.Y.T. van de Meerakker, G.C. Groenenboom, G. Meijer,
Science 313, 1617 (2006).
[3] M. Kirste, X. Wang, H.C. Schewe, G. Meijer, K. Liu, A. van der Avoird, L.M.C.
Janssen, K.B. Gubbels, G.C. Groenenboom, S.Y.T. van de Meerakker,
Science 338, 1060 (2012).
[4] A. von Zastrow, J. Onvlee, S.N. Vogels, G.C. Groenenboom, A. van der Avoird,
S.Y.T. van de Meerakker, Nature Chemistry 6, 216 (2014).
[5] S.N. Vogels, J. Onvlee, A. von Zastrow, G.C. Groenenboom, A. van der Avoird,
S.Y.T. van de Meerakker, Phys. Rev. Lett. 113, 263202 (2014).