Super-conducting magnets

Frank Knoll/ M S / Min Proc / President, Carpco, Inc., Jacksonville, EL. (Super Conducting Magnetic Separation and Electrostatic Separation)... 

The advances in NMR spectroscopy in the last ten years were enormous. Thus, almost all laboratories which produce papers are equipped with SCM (Super Conducting Magnet) instruments with 400-500 MHz magnets, and 2D or multidimensional NMR experiments are now routinely employed. In addition, solid-state NMR and NMR imaging (MRI) have widened their scope to a considerable extent. 29 Si NMR has enjoyed this general progress. 

As mentioned in Section 6.6, the author s group studied MFEs on a singlet-sensitized photodecompostion reaction of dibenzoylperoxide in toluene at room temperature with a small super-conducting magnets, whose maximum field was 4.3 T [1]. We found that the field of 4.3 T decreased the yield (Fc )of the cage product (phenyl benzoate) by 8+3 % and... 

Boxer s group [2] first made a ns-laser photolysis apparatus with a super-conducting magnet. The sample was excited at 532 or 600 nm with a frequency-doubled YAG pumped dye laser (8ns, fwhm) and was probed at 860 nm with a laser diode. The maximum field of their magnet was 5 T. With this apparatus, they measured the quantum yield of triplet states (detected optically in quinone-depleted photosynthetic reaction centers (RCs) from R. spheroids, R-26 mutant, as a function of applied magnetic strength and temperature. The reaction scheme for qinone-depleted RCs is shown in Fig. 12.1. Here, the singlet and triplet radical-ion pair (RIP) are represented by [D" A ] and [D A ], respectively, and the rate constants of the S-T conversion of RIP, the recombination from [D A ], and the recombination from [D A ] are denoted by hsT, ks, and kj, respectively. 

Johnson, L. F., Nuclear magnetic resonance with super-conducting magnets. Anal. Chem. 43, 28A-36A (1971). 

The first rule of NMR is Crap in equals crap out. It does not matter how many millions you spend on a super conducting magnet, nor how carefully you isolate vibrations, eliminate electromagnetic noise, stabilize temperatures, train your... 

Ideally one would like the ability to manipulate molecules in the same fashion as atoms. However, without the ability to laser cool, the requirements of the initial trap become much more involved. Instead of the initial trap being at lmK, we now need the initial trap to be in the 10 to 100 mK range. Most closed shell ground state molecules have small Zeeman shifts which makes magnetic trapping, even with super-conducting magnets... 

FT-ICR mass filter cavities are 2 to 5 cm in size. The associated hardware, which includes a super conducting magnet required to produce fields of 7-12 Tesla, and so on, significantly increases the size of such instruments such that they will fill a small room. A schematic diagram of a typical FT-ICR mass filter cavity is depicted in Figure 4.13. 

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