Issue 33, 2014

Diffusive and rotational dynamics of condensed n-H2 confined in MCM-41

Abstract

In this paper, we report an inelastic neutron scattering study of liquid and solid n-H2 confined within MCM-41. This is a high surface area, mesoporous silica glass with a narrow pore size distribution centered at 3.5 nm. The scattering data provides information about the diffusive and rotational dynamics of the adsorbed n-H2 at low temperatures. In the liquid state, the neutron scattering data demonstrates that only a fraction of the adsorbed o-H2 is mobile on the picosecond time scale. This mobile fraction undergoes liquid-like jump diffusion, and values for the residence time τ and effective mean-squared displacement 〈u2〉 are reported as a function of pore filling. In the solid state, the rotational energy levels of adsorbed H2 are strongly perturbed from their free quantum rotor behavior in the bulk solid. The underlying orientational potential of the hindered rotors is due to the surface roughness and heterogeneity of the MCM-41 pore walls. This potential is compared to the hindering potential of other porous silicas, such as Vycor. Strong selective adsorption makes the interfacial layer rich in o-H2, leaving the inner core volume consisting of a depleted mixture of o-H2 and p-H2.

Graphical abstract: Diffusive and rotational dynamics of condensed n-H2 confined in MCM-41

Supplementary files

Article information

Article type
Paper
Submitted
24 May 2014
Accepted
07 Jul 2014
First published
10 Jul 2014

Phys. Chem. Chem. Phys., 2014,16, 17960-17974

Author version available

Diffusive and rotational dynamics of condensed n-H2 confined in MCM-41

T. R. Prisk, M. S. Bryan and P. E. Sokol, Phys. Chem. Chem. Phys., 2014, 16, 17960 DOI: 10.1039/C4CP02281E

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.

Social activity

Spotlight

Advertisements