Isotopes resonance

The magnetogyric ratio is different for each isotope thus at a constant Bq, different isotopes resonate at different frequencies. For example, if Bq = 14 T, H atoms resonate at 600 MHz and atoms resonate at 150 MHz. When atoms are placed in a static magnetic field, their electronic environments create small perturbations in the effective magnetic field sensed by nuclei in slightly different local environments. The... 

Because of the high negative ( -values for the [pn) reactions (Table 5), particularly for the more abundant isotopes, resonances in these reactions have been found only under conditions of relatively poor resolution, e.g. with cyclotron beams (Blaser et al. ). Above the [pn) threshold the total width of resonance levels is in any case expected to increase since neutron emission is not hindered by the Coulomb barrier, and most of the narrow resonances observed are seen below this energy. 

Fig. 38. Curve prepared by D. J. Hughes and J. A. Harvey (submitted for publication in the Physical Review) combining the results of the measured distribution of values for many isotopes. Resonances having very small...

Mills, R. L. Pharmaceuticals and apparatus based on Moessbauer isotopic resonant absorption of y... 

Mills, R. L. Pharmaceuticals and apparatus based on Moessbauer isotopic resonant absorption of Y emission (MIRAGE) providing diagnosis and selective tissue necrosis. Can. Pat. Appl. CA 2005039,1991. 

Figrue BTl 1.1 shows the range of radiolfequencies where resonances may be expected, between 650 and 140 MHz, when Bq = 14.1 T, i.e. when the H resonance frequency is 600 MHz. There is one bar per stable isotope. Its width is the reported chemical shift range (Bl.11.5) for that isotope, and its height corresponds to the log of the sensitivity at the natural abundance of the isotope, covering about six orders of magnitude. The... 

Figure Bl.11.1. Resonance frequencies for different nuclei in a field of 14.1 T. Widths indicate the quoted range of shifts for each nucleus, and heights mdicate relative sensitivities at the natural isotopic abundance, on a log scale covering approximately six orders of magnitude. Nuclei resonatmg below 140 MHz are not shown.

IR-UV double resonance also selective for S and C Reaction of both Isotopes with high selectivity (high fluence)... 

Concerning N-magnetic resonance, Boejesen et at. (113) have measured the following coupling constants on a sample of thiazole enriched in this isotope ... 

FTICR. Fourier-transform ion cyclotron resonance GC/IRMS. gas chromatography isotope ratio mass spectrometry... 

Benzoates. The selective debenzoylation of sucrose octabenzoate [2425-84-5] using isopropylamine in the absence of solvents caused deacylation in the furanose ring to give 2,3,4,6,1/3/6 -hepta- and 2,3,4,6,1/6 -hexa-O-benzoyl-sucroses in 24.1 and 25.4% after 21 and 80 hours, respectively (54). The unambiguous assignment of partially benzoylated sucrose derivatives was accompHshed by specific isotopic labeling techniques (54). Identification of any benzoylated sucrose derivative can thus be achieved by comparison of its C-nmr carbonyl carbon resonances with those of the assigned octabenzoate derivative after benzoylation with 10 atom % benzoyl—carbonyl chloride in pyridine. 

Nuclear Magnetic Resonance. AH three hydrogen isotopes have nuclear spins, I 7 0, and consequently can all be used in nmr spectroscopy (Table 4) (see Magnetic spin resonance). Tritium is an even more favorable nucleus for nmr than is H, which is by far the most widely used nucleus in nmr spectroscopy. The radioactivity of T and the ensuing handling problems are a deterrent to widespread use for nmr. Considerable progress has been made in the appHcations of tritium nmr (23,24). 

Table 4. Nuclear Magnetic Resonance Properties of Hydrogen Isotopes...

Isotope Nuclear spin Resonance frequency, MH2 Relative sensitivity Magnetic moment, 10 j/t ... 

Isotope shifts for most elements are small in comparison with the bandwidth of the pulsed lasers used in resonance ionization experiments, and thus all the isotopes of the analyte will be essentially resonant with the laser. In this case, isotopic analysis is achieved with a mass spectrometer. Time-of flight mass spectrometers are especially well-suited for isotopic analysis of ions produced by pulsed resonance ionization lasers, because all the ions are detected on each pulse. 

When, in NRA, resonances are used, and the depth profile of an isotope A is obtained from the excitation curve N(Eq), the reaction depth x is given by the requirement that projectiles incident with energy Eq are slowed down to the resonance energy Fr at X, which leads to ... 

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