Characterisation and modeling of a pulsed molecular beam

Abstract

Standard techniques used in real-time reaction dynamics experiments, namely photoionization by a pulsed laser and velocity imaging are applied to document the time dependent velocity distribution of 2-hydroxypyridine (2-HP) molecules in a pulsed beam where 2-HP is seeded in either helium or argon. The purpose is to identify features which cannot be assigned to a pure free molecular (effusive in the present case) or a pure continuum (supersonic here) flow regime. The beam is generated in a two stage expansion, where the first stage is driven by a pulsed valve. The experimental work is complemented by simulations. Two phenomena retain the attention: (i) a slow return to the effusive flow regime after the valve opening has generated an intense supersonic flow; (ii) development of a shock wave a short time after the valve opening.

GRAPHICAL ABSTRACT

KEYWORDS:

• Molecular beams
• transition flow
• velocity map imaging
• pulsed valve
• chock wave

Acknowledgments

The authors kindly thank David Parker and André Eppink for their help in building our VMI.

Disclosure statement

No potential conflict of interest was reported by the authors.

ORCID

A. Lietard http://orcid.org/0000-0003-4961-3409

G. Gallician http://orcid.org/0000-0001-8600-3269

M.-A. Gaveau http://orcid.org/0000-0003-3922-5015

M. Briant http://orcid.org/0000-0003-3745-9061

B. Soep http://orcid.org/0000-0002-8841-7120

J.-M. Mestdagh http://orcid.org/0000-0002-7638-4181

L. Poisson http://orcid.org/0000-0002-7131-968X

Additional information

Funding

The authors thank D. Guillaumet, M. Perdrix and Dr. O. Gobert for running the SLIC/LUCA laser facility. Financial support is acknowledged from the Agence Nationale pour la Recherche [grant number ANR-14-CE32-0010 XTASE].