Magnet, spectrometer oscillator frequencies

The original method employed was to scan eitiier the frequency of the exciting oscillator or to scan the applied magnetic field until resonant absorption occiined. Flowever, compared to simultaneous excitation of a wide range of frequencies by a short RF pulse, the scanned approach is a very time-inefficient way of recording the spectrum. Flence, with the advent of computers that could be dedicated to spectrometers and efficient Fourier transfomi (FT) algoritluns, pulsed FT NMR became the nomial mode of operation. 

Development of Dosimeter Materials. - 4.2.1 Quantitative ESR and Intensity Standards of Mn1+ and CuS04.5H20. An ESR spectrometer consists of vacuum tube amplifier and a Klystron oscillator with thermal noise and frequency drift. Hence, an inherent standard of Mn2+ was used in ESR dating of carbonate stalactites,8 and patented as a standard in ESR radiation dosimetry in 1980.102 The standard sample of MgO with Mn2+ is frequently used for calibration of -factor and the magnetic field as well as for radiation dosimetry.103... 

Ultraviolet and visible spectra were recorded with a Beckman DK-2 or Cary 14 spectrophotometer. ESR spectra were measured with a Varian model 4500 ESR spectrometer with 100-kHz field-modulation and detection. The klystron frequency was measured with a transfer oscillator and a frequency counter. The magnetic field was measured by a proton gauss meter monitored by the same frequency counter. 

Facilities for a variety of multiple-resonance experiments, including broad-band, homo- or hetero-nuclear decoupling, are now generally built into the spectrometer, instead of being provided by auxiliary audio-oscillators. Oscilloscopes for optimization of magnetic-field homogeneity, precalibrated recorder-charts, and frequency counters for accurate calibration of charts and frequencies for multiple... 

An NMR spectrometer can only be configured to examine one isotope at a time, resulting in a homonu-clear spectrum. Because the magnetic field strength B0 is fixed, each different isotope requires a different Bi oscillator (operating) frequency v0. 

The magnetogyric ratio of a free electron is approximately 657 times that of a proton. Modem EPR spectrometers use a microwave generator (klystron) as the source of electromagnetic radiation (i.e., the oscillating magnetic field), with operating frequencies in the range 1-100 GHz (1 GHz = 103 MHz = 109 Hz) 9.5 GHz (the so-called A-band) is perhaps the most common. 

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