Issue 17, 1993

Alignment of diatomic molecules in a free-jet expansion

Abstract

We describe the results of a polarised fluorescence study of the spatial distribution of alignment of I2 molecules seeded in a free jet of helium gas. We have observed that molecular alignment tends to increase towards the edges of the jet in a manner reminiscent of that observed in fluid flow. This suggests that the alignment of seeded species is induced during the fluid-like flow region that characterises the supersonic jet expansion. The distribution of alignment results from the spatial distribution of shear forces, a consequence of the transverse velocity gradients. This alignment is not lost in the gas-dynamic region since collisions that change the m quantum number are extremely inefficient. This interpretation suggests that the assumption of inviscid flow in the continuum region is inappropriate for discussing molecular alignment though might be valid under high Reynolds number conditions. It may also indicate that careful design of the nozzle or capillary might give internal shear fields that would lead to molecular orientation along with or instead of molecular alignment.

Article information

Article type
Paper

J. Chem. Soc., Faraday Trans., 1993,89, 3217-3221

Alignment of diatomic molecules in a free-jet expansion

H. J. Saleh and A. J. McCaffery, J. Chem. Soc., Faraday Trans., 1993, 89, 3217 DOI: 10.1039/FT9938903217

To request permission to reproduce material from this article, please go to the Copyright Clearance Center request page.

If you are an author contributing to an RSC publication, you do not need to request permission provided correct acknowledgement is given.

If you are the author of this article, you do not need to request permission to reproduce figures and diagrams provided correct acknowledgement is given. If you want to reproduce the whole article in a third-party publication (excluding your thesis/dissertation for which permission is not required) please go to the Copyright Clearance Center request page.

Read more about how to correctly acknowledge RSC content.

Spotlight

Advertisements