Electron Spin Polarization Transfer to ortho-H-2 by Interaction of para-H-2 with Paramagnetic Species: A Key to a Novel para -> ortho Conversion Mechanism

Abstract : We report that at ambient temperature and with 100% enriched para-hydrogen (p-H-2) dissolved in organic solvents, paramagnetic spin catalysis of para -> ortho hydrogen conversion is accompanied at the onset by a negative ortho-hydrogen (o-H-2) proton NMR signal. This novel finding indicates an electron spin polarization transfer, and we show here that this can only occur if the H-2 molecule is dissociated upon its transient adsorption by the paramagnetic catalyst. Following desorption, o-H-2 is created until the thermodynamic equilibrium is reached. A simple theory confirms that in the presence of a static magnetic field, the hyperfine coupling between unpaired electrons and nuclear spins is responsible for the observed polarization transfer. Owing to the negative electron gyromagnetic ratio, this explains the experimental results and ascertains an as yet unexplored mechanism for para -> ortho conversion. Finally, we show that the recovery of o-H-2 magnetization toward equilibrium can be simply modeled, leading to the para -> ortho conversion rate.
Type de document :
Article dans une revue
Journal of Physical Chemistry Letters, American Chemical Society, 2015, 6 (9), pp.1611-1615. 〈10.1021/acs.jpclett.5b00518〉
Liste complète des métadonnées

https://hal.univ-lorraine.fr/hal-01521911
Contributeur : Crm2 Ul <>
Soumis le : vendredi 12 mai 2017 - 14:44:13
Dernière modification le : jeudi 11 janvier 2018 - 06:26:02

Identifiants

Collections

Citation

Camilla Terenzi, Sabine Bouguet-Bonnet, Daniel Canet. Electron Spin Polarization Transfer to ortho-H-2 by Interaction of para-H-2 with Paramagnetic Species: A Key to a Novel para -> ortho Conversion Mechanism. Journal of Physical Chemistry Letters, American Chemical Society, 2015, 6 (9), pp.1611-1615. 〈10.1021/acs.jpclett.5b00518〉. 〈hal-01521911〉

Partager

Métriques

Consultations de la notice

43