Using a direct simulation Monte Carlo approach to model collisions in a buffer gas cell.
A direct simulation Monte Carlo (DSMC) method is applied to model collisions between He buffer gas atoms and ammonia molecules within a buffer gas cell. State-to-state cross sections, calculated as a function of the collision energy, enable the inelastic collisions between He and NH3to be considered explicitly. The inclusion of rotational-state-changing collisions affects the translational temperature of the beam, indicating that elastic and inelastic processes should not be considered in isolation. The properties of the cold molecular beam exiting the cell are examined as a function of the cell parameters and operating conditions; the rotational and translational energy distributions are in accord with experimental measurements. The DSMC calculations show that thermalisation occurs well within the typical 10-20 mm length of many buffer gas cells, suggesting that shorter cells could be employed in many instances-yielding a higher flux of cold molecules.
Department of Chemistry, University of Oxford, Chemistry Research Laboratory, 12 Mansfield Road, Oxford OX1 3TA, United Kingdom.
Maximilian J
MJ
Doppelbauer
Department of Chemistry, University of Oxford, Chemistry Research Laboratory, 12 Mansfield Road, Oxford OX1 3TA, United Kingdom.
Otto
O
Schullian
Service de Chimie Quantique et Photophysique, Université Libre de Bruxelles (ULB), CP 160/09, 50 Ave. F.D. Roosevelt, 1050 Brussels, Belgium.
Jerome
0000000261421509
J
Loreau
Service de Chimie Quantique et Photophysique, Université Libre de Bruxelles (ULB), CP 160/09, 50 Ave. F.D. Roosevelt, 1050 Brussels, Belgium.
Nathalie
0000000305909646
N
Vaeck
Institute for Molecules and Materials, Radboud University, Heyendaalseweg 135, 6525 AJ Nijmegen, The Netherlands.
Ad
000000031856240X
A
van der Avoird
Department of Chemistry, University of Oxford, Chemistry Research Laboratory, 12 Mansfield Road, Oxford OX1 3TA, United Kingdom.
Christopher J
0000000349930156
CJ
Rennick
University of Birmingham, Edgbaston, Birmingham B15 2TT, United Kingdom.
Timothy P
0000000252856308
TP
Softley
Department of Chemistry, University of Oxford, Chemistry Research Laboratory, 12 Mansfield Road, Oxford OX1 3TA, United Kingdom.
Brianna R
BR
Heazlewood