Toroid cavity autoclave

Another class of toroidal NMR probes is formed by toroid cavity detectors (TCD) [31]. These TCD have been mounted into cylindrical metallic autoclaves to study spin relaxation effects of gases under pressure [31]. If the toroid cavity detector is the metallic pressure vessel itself it is called a toroid cavity autoclave (TCA) probe [32, 33]. These probes can be tuned to higher resonance frequencies than TCDs and also show better spectral resolution [29]. Figure 2.12 shows the design of a TCA where the autoclave body is built from phosphorus bronze [33] keeping the field distortions of the magnetic field Bq, induced by susceptibility mismatches... 

Figure 2.12 Exploded (left) and assembled (right) view of a toroid cavity autoclave probe for in situ investigations under high gas pressures or in supercritical fluids. Autoclave base (A) and autoclave body (P-bronze, B) thermocouple (C) coaxial heater (D) PTFE ring (E) central conductor (Cu/Be ring, F) nonmagnetic pin from male coaxial connection (G) RF feedthrough (from Rathke [28], H) base-plate (MACOR, I) fixing screws (P-bronze, J) PEEK capillary (l<) ceramic ball (Si3N4, L) PTFE seal (M).

R 527 H. G. Niessen, P. Trautner, R. Backhausen and K. Woelk, Recent Developments in Toroid Cavity Autoclave Engineering , Concepts Magn. Reson., 2003,16B, 15... 

The toroidal pressure probe, introduced in 1989 by Rathke and coworkers [249, 250], has been modified by Woelk and coworkers [249, 251], who have used a toroid cavity NMR autoclave for high pressure PHIP NMR experiments. Figure 1.43 shows the PHIP spectrum of the [Rh(norbornadiene)(PPh3)2]PF6-catalyzed hydrogenation of 1,4-diphenylbutadiyne with 40 bar of 50% emiched para-H2 [252]. The spectrum from the same reaction at ambient H2 pressure is shown in the inset [253]. The two absorption/emission PHIP patterns in both spectra indicate that para-H2 is transferred pairwise during the catalytic cycle. 

Woelk and coworkers [252, 270] have provided a detailed view into the activation and transfer of the dihydrogen molecule during hydrogenations in SCCO2, using PHIP and their toroid cavity NMR autoclave. For the asymmetric hydrogenation... 

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