Nuclear magnetic resonance of 3He dissolved in vitreous silica

✍ Scribed by R.K. Mazitov; P. Diehl; R. Seydoux

• Publisher: Elsevier Science
• Year: 1993
• Tongue: English
• Weight: 602 KB
• Volume: 201
• Category: Article
• ISSN: 0009-2614
• DOI: 10.1016/0009-2614(93)85114-4

✦ Synopsis

For the ftrst time 'He gas dissolved in solids (pyrex and suprasil glasses) has been studied by NMR. The chemical shifts are mainly determined by interaction with diamagnetic atoms of the glass structure and not by magnetic interaction with Fe'+ ions. In pyrex the relaxation times at 25°C are: T, ('He) = 65 f 6.5 ms, T2 ('He) = 1.1 f 0.1 ms and the activation energy for relaxation isE,(T,)=E,(T,)=3.4+0.3 kJ/mol (-70 to 100'C). In suprasil T,('He)=l.l+O.l s (25'(Z), J&=18&2 kJ/mol (-40 to 20°C) and r, ('He) = 370+ 40 s (OOC). The relaxation times in both glasses are determined by magnetic dipole-dipole interaction, in Pyrex with Fe'+ ions modulated by spin-flip and in suprasil with unpaired electrons of defects in the glass structure modulated by the fast diffusion of helium atoms. The estimated values of distances of closest approach of diffusing 3He atoms to Fe'+ ions in Pyrex and to defects in suprasil are _ 5 and m 3 A, respectively.