Pulsed saturation recovery 250 MHz electron paramagnetic resonance spectrometer

Quine, Richard W.

doi:10.1002/cmr.b.20043

Cited by 6 publications

(3 citation statements)

References 30 publications

(28 reference statements)

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“…A 16-pulse phase cycling sequence was used to minimize the impact of the FID on the spin echo decays. Room-temperature values of T 1 and T 2 also were measured on locally constructed spectrometers operating at 2.76, 1.9, and 0.25 GHz . Phase cycling and a magnetic object in the magnetic field (or a field gradient) were used to minimize the impact of the FID.…”

Section: Methodsmentioning

confidence: 99%

Electron Spin Relaxation in x-Lithium Phthalocyanine

Sato

Dalton

et al. 2007

J. Phys. Chem. B

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Continuous-wave linewidths and spin susceptibilities, spin-spin relaxation rates (1/T2), and spin-lattice relaxation rates (1/T1) for two sources of x-LiPc were measured at 9.5 GHz between 15 and 298 K. Relaxation rates at 34 GHz were measured between 80 and 298 K. Room-temperature relaxation rates also were measured at 250 MHz, 1.9 GHz, and 2.76 GHz. The temperature dependences of linewidths and spin susceptibilities are characteristic of 1-D organic conductors. The ratio of populations of localized and delocalized electrons varies with sample preparation. For a single needle between 15 and about 200 K, 1/T2 is higher for the parallel orientation, but 1/T1 is higher for the perpendicular orientation, consistent with predictions based on dipolar interactions. Between about 60 and 150 K, which is the temperature regime in which spin susceptibility is changing rapidly with temperature, 1/T1 exhibits a non-monotonic dependence on temperature and is lower at 34 GHz than at 9.5 GHz. In other organic conductors, this dependence has been attributed to a bottleneck mechanism of relaxation. At higher temperatures, 1/T1 becomes less orientation-dependent. At room temperature, T1 increases rapidly between 250 MHz (3.0 micros) and 2.76 GHz (6.3 micros) and then shows less frequency dependence up to 34 GHz (9.8 micros). The relaxation rate near room temperature might have a substantial contribution from spin hopping perpendicular to the stacking axis of the molecules.

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Section: Methodsmentioning

confidence: 99%

Electron Spin Relaxation in x-Lithium Phthalocyanine

Sato

Dalton

et al. 2007

J. Phys. Chem. B

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“…9,10 Purpose-built saturation recovery spectrometers have been reported by Quine et al, 11 Beck et al, 12 and Mailer et al 13 at X-band and by Quine et al at L-band 14 and 250 MHz. 15 Saturation recovery is available as an option for the Bruker Elexsys E580 spectrometer that uses an electron-electron double resonance (ELDOR) accessory and a 5 W solid state amplifier. Recently, digital components such as arbitrary waveform generators (AWG) and fast digitizers have made it possible to re-envision continuous wave saturation recovery spectrometers.…”

Section: Articlementioning

confidence: 99%

An x-band continuous wave saturation recovery electron paramagnetic resonance spectrometer based on an arbitrary waveform generator

McPeak

Quine

Eaton

2019

Review of Scientific Instruments

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An X-band (ca. 9-10 GHz) continuous wave saturation recovery spectrometer to measure electron spin-lattice relaxation (T 1) was designed around an arbitrary waveform generator (AWG). The AWG is the microwave source and is used for timing of microwave pulses, generation of control signals, and digitizer triggering. Use of the AWG substantially simplifies the hardware in the bridge relative to that in conventional spectrometers and decreases the footprint. The bridge includes selectable paths with different power amplifications to permit experiments requiring hundreds of milliwatts to fractions of nanowatts for the pump and observe periods. The signal is detected with either a single or quadrature-output double balanced mixer. The system can operate with reflection or crossed-loop resonators. The source noise from the AWG was decreased by addition of a Wenzel high-stability clock. The source is sufficiently stable that automatic frequency control is not needed. The spectrometer was tested with samples that contained 1 × 10 15 to 8 × 10 17 spins and have T 1 between a few hundred ns and hundreds of µs. Excellent signal-to-noise ratio was obtained with acquisition times of 2-90 s. Signal-to-noise performance is similar to that of a conventional saturation recovery spectrometer with a solid-state source. The stability and data reproducibility are better than with conventional sources. With replacement of frequency-sensitive components, this spectrometer can be used to perform saturation recovery measurements at any frequency within the range of the AWG.

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“…Initially, Abs and Abs D signals measured with our locally designed and built 250MHz spectrometer [15] had different amplitudes. Careful analysis of the electrical circuit responsible for phase-sensitive detection (see Fig.1) revealed that the 90° splitter (right hand side of Fig.…”

Section: Instrumental Considerationmentioning

confidence: 99%

Combining absorption and dispersion signals to improve signal-to-noise for rapid-scan EPR imaging

Tseitlin

Quine

Rinard

et al. 2010

Journal of Magnetic Resonance

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Direct detection of the rapid scan EPR signal with quadrature detection and without automatic frequency control provides both the absorption and dispersion components of the signal. The use of a cross-loop resonator results in similar signal-to-noise in the two channels. The dispersion signal can be converted to an equivalent absorption signal by means of Kramers-Kronig relations. The converted signal is added to the directly-measured absorption signal. Since the noise in the two channels is not correlated, this procedure increases the signal-to-noise ratio of the resultant absorption signal by up to a factor of √2. The utility of this method was demonstrated for 2D spectral-spatial imaging of a phantom containing 3 tubes of LiPc with different oxygen concentrations and therefore different linewidths.

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Pulsed saturation recovery 250 MHz electron paramagnetic resonance spectrometer

Cited by 6 publications

References 30 publications

Electron Spin Relaxation in x-Lithium Phthalocyanine

Electron Spin Relaxation in x-Lithium Phthalocyanine

An x-band continuous wave saturation recovery electron paramagnetic resonance spectrometer based on an arbitrary waveform generator

Combining absorption and dispersion signals to improve signal-to-noise for rapid-scan EPR imaging

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