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Campanella AJ, Üngör Ö, Zadrozny JM. Quantum Mimicry With Inorganic Chemistry. COMMENT INORG CHEM 2023; 44:11-53. [PMID: 38515928 PMCID: PMC10954259 DOI: 10.1080/02603594.2023.2173588] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/15/2023]
Abstract
Quantum objects, such as atoms, spins, and subatomic particles, have important properties due to their unique physical properties that could be useful for many different applications, ranging from quantum information processing to magnetic resonance imaging. Molecular species also exhibit quantum properties, and these properties are fundamentally tunable by synthetic design, unlike ions isolated in a quadrupolar trap, for example. In this comment, we collect multiple, distinct, scientific efforts into an emergent field that is devoted to designing molecules that mimic the quantum properties of objects like trapped atoms or defects in solids. Mimicry is endemic in inorganic chemistry and featured heavily in the research interests of groups across the world. We describe a new field of using inorganic chemistry to design molecules that mimic the quantum properties (e.g. the lifetime of spin superpositions, or the resonant frequencies thereof) of other quantum objects, "quantum mimicry." In this comment, we describe the philosophical design strategies and recent exciting results from application of these strategies.
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Affiliation(s)
- Anthony J. Campanella
- Department of Chemistry, Colorado State University, Fort Collins, CO, USA, Address: 200 W. Lake St, Campus Delivery 1872, Fort Collins, CO 80523, USA
| | - Ökten Üngör
- Department of Chemistry, Colorado State University, Fort Collins, CO, USA, Address: 200 W. Lake St, Campus Delivery 1872, Fort Collins, CO 80523, USA
| | - Joseph M. Zadrozny
- Department of Chemistry, Colorado State University, Fort Collins, CO, USA, Address: 200 W. Lake St, Campus Delivery 1872, Fort Collins, CO 80523, USA
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Halpern HJ, Epel BM. Going Low in a World Going High: The Physiologic Use of Lower Frequency Electron Paramagnetic Resonance. APPLIED MAGNETIC RESONANCE 2020; 51:887-907. [PMID: 33776216 PMCID: PMC7992374 DOI: 10.1007/s00723-020-01261-7] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/05/2020] [Revised: 08/20/2020] [Indexed: 05/26/2023]
Abstract
Yakov Sergeevich Lebedev was a pioneer in high frequency EPR, taking advantage of the separation of g-factor anisotropy effects from nuclear hyperfine splitting and the higher frequency molecular motion sensitivity from higher frequency measurements8. This article celebrates a second EPR subfield in which Prof. Lebedev pioneered, EPR imaging. 9 We celebrate the clinical enhancements that are suggested in this low frequency work and imaging application to animal physiology at lower-than-standard EPR frequencies.
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Affiliation(s)
- Howard J Halpern
- Center for EPR imaging in vivo physiology, University of Chicago
- Department of Radiation and Cellular Oncology, Unversity of Chicago
| | - Boris M Epel
- Center for EPR imaging in vivo physiology, University of Chicago
- Department of Radiation and Cellular Oncology, Unversity of Chicago
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Buchanan LA, Rinard GA, Quine RW, Eaton SS, Eaton GR. Tabletop 700 MHz electron paramagnetic resonance imaging spectrometer. CONCEPTS IN MAGNETIC RESONANCE. PART B, MAGNETIC RESONANCE ENGINEERING 2018; 48B:e21384. [PMID: 30804714 PMCID: PMC6386469 DOI: 10.1002/cmr.b.21384] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/02/2018] [Accepted: 08/11/2018] [Indexed: 06/05/2023]
Abstract
Low frequency electron paramagnetic resonance imaging is a powerful tool to non-invasively measure the physiological status of tumors. Here, we report on the design and functionality of a rapid scan and pulse table-top imaging spectrometer based around an arbitrary waveform generator and 25mm cross-loop resonator operating at 700 MHz. Two and four-dimensional rapid scan spectral-spatial images are presented. This table-top imager is a prototype for future pre-clinical imagers.
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Affiliation(s)
- Laura A. Buchanan
- Department of Chemistry and Biochemistry and Center for EPR Imaging of In Vivo Physiology, University of
Denver, Denver, CO 80210
| | - George A. Rinard
- School of Engineering and Computer Science and Center for EPR Imaging of In Vivo Physiology, University of
Denver, Denver, CO 80210
| | - Richard W. Quine
- School of Engineering and Computer Science and Center for EPR Imaging of In Vivo Physiology, University of
Denver, Denver, CO 80210
| | - Sandra S. Eaton
- Department of Chemistry and Biochemistry and Center for EPR Imaging of In Vivo Physiology, University of
Denver, Denver, CO 80210
| | - Gareth R. Eaton
- Department of Chemistry and Biochemistry and Center for EPR Imaging of In Vivo Physiology, University of
Denver, Denver, CO 80210
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Shi Y, Quine RW, Rinard GA, Buchanan L, Eaton SS, Eaton GR, Epel B, Seagle SW, Halpern HJ. Triarylmethyl Radical: EPR Signal to Noise at Frequencies between 250 MHz and 1.5 GHz and Dependence of Relaxation on Radical and Salt Concentration and on Frequency. ACTA ACUST UNITED AC 2016; 231:923-937. [PMID: 28392627 DOI: 10.1515/zpch-2016-0813] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
In vivo oximetry by pulsed electron paramagnetic resonance is based on measurements of changes in electron spin relaxation rates of probe molecules, such as the triarylmethyl radicals. A series of experiments was performed at frequencies between 250 MHz and 1.5 GHz to assist in the selection of an optimum frequency for oximetry. Electron spin relaxation rates for the triarylmethyl radical OX063 as a function of radical concentration, salt concentration, and resonance frequency were measured by electron spin echo 2-pulse decay and 3-pulse inversion recovery in the frequency range of 250 MHz-1.5 GHz. At constant OX063 concentration, 1/T1 decreases with increasing frequency because the tumbling dependent processes that dominate relaxation at 250 MHz are less effective at higher frequency. 1/T2 also decreases with increasing frequency because 1/T1 is a significant contribution to 1/T2 for trityl radicals in fluid solution. 1/T2-1/T1, the incomplete motional averaging contribution to 1/T2, increases with increasing frequency. At constant frequency, relaxation rates increase with increasing radical concentration due to contributions from collisions that are more effective for 1/T2 than 1/T1. The collisional contribution to relaxation increases as the concentration of counter-ions in solution increases, which is attributed to interactions of cations with the negatively charged radicals that decrease repulsion between trityl radicals. The Signal-to-Noise ratio (S/N) of field-swept echo-detected spectra of OX063 were measured in the frequency range of 400 MHz-1 GHz. S/N values, normalized by √Q, increase as frequency increases. Adding salt to the radical solution decreased S/N because salt lowers the resonator Q. Changing the temperature from 19 to 37 °C caused little change in S/N at 700 MHz. Both slower relaxation rates and higher S/N at higher frequencies are advantageous for oximetry. The potential disadvantage of higher frequencies is the decreased depth of penetration into tissue.
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Affiliation(s)
- Yilin Shi
- Department of Chemistry and Biochemistry and Center for EPR Imaging In Vivo Physiology, University of Denver, Denver, CO 80210, USA
| | - Richard W Quine
- School of Engineering and Computer Science and Center for EPR Imaging In Vivo Physiology, University of Denver, Denver, CO 80210, USA
| | - George A Rinard
- School of Engineering and Computer Science and Center for EPR Imaging In Vivo Physiology, University of Denver, Denver, CO 80210, USA
| | - Laura Buchanan
- Department of Chemistry and Biochemistry and Center for EPR Imaging In Vivo Physiology, University of Denver, Denver, CO 80210, USA
| | - Sandra S Eaton
- Department of Chemistry and Biochemistry and Center for EPR Imaging In Vivo Physiology, University of Denver, Denver, CO 80210, USA
| | - Gareth R Eaton
- Gareth R. Eaton, Department of Chemistry and Biochemistry and Center for EPR Imaging In Vivo Physiology, University of Denver, Denver, CO 80210, USA
| | - Boris Epel
- Department of Radiation and Cellular Oncology and Center for EPR Imaging In Vivo Physiology, University of Chicago, Chicago, IL 60637, USA
| | - Simone Wanless Seagle
- Department of Radiation and Cellular Oncology and Center for EPR Imaging In Vivo Physiology, University of Chicago, Chicago, IL 60637, USA
| | - Howard J Halpern
- Department of Radiation and Cellular Oncology and Center for EPR Imaging In Vivo Physiology, University of Chicago, Chicago, IL 60637, USA
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Elnaggar SY, Tervo R, Mattar SM. Optimal dielectric and cavity configurations for improving the efficiency of electron paramagnetic resonance probes. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2014; 245:50-57. [PMID: 24937043 DOI: 10.1016/j.jmr.2014.05.011] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/21/2014] [Revised: 05/24/2014] [Accepted: 05/26/2014] [Indexed: 06/03/2023]
Abstract
An electron paramagnetic resonance (EPR) spectrometer's lambda efficiency parameter (Λ) is one of the most important parameters that govern its sensitivity. It is studied for an EPR probe consisting of a dielectric resonator (DR) in a cavity (CV). Expressions for Λ are derived in terms of the probe's individual DR and CV components, Λ1 and Λ2 respectively. Two important cases are considered. In the first, a probe consisting of a CV is improved by incorporating a DR. The sensitivity enhancement depends on the relative rather than the absolute values of the individual components. This renders the analysis general. The optimal configuration occurs when the CV and DR modes are nearly degenerate. This configuration guarantees that the probe can be easily coupled to the microwave bridge while maintaining a large Λ. It is shown that for a lossy CV with a small quality factor Q2, one chooses a DR that has the highest filling factor, η1, regardless of its Λ1 and Q1. On the other hand, if the CV has a large Q2, the optimum DR is the one which has the highest Λ1. This is regardless of its η1 and relative dielectric constant, ɛr. When the quality factors of both the CV and DR are comparable, the lambda efficiency is reduced by a factor of 2. Thus the signal intensity for an unsaturated sample is cut in half. The second case is the design of an optimum shield to house a DR. Besides preventing radiation leakage, it is shown that for a high loss DR, the shield can actually boost Λ above the DR value. This can also be very helpful for relatively low efficiency dielectrics as well as lossy samples, such as polar liquids.
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Affiliation(s)
- Sameh Y Elnaggar
- Department of Electrical and Computer Engineering, University of New Brunswick, Fredericton, New Brunswick, E3B 5A3 Canada
| | - Richard Tervo
- Department of Electrical and Computer Engineering, University of New Brunswick, Fredericton, New Brunswick, E3B 5A3 Canada
| | - Saba M Mattar
- Department of Chemistry and Centre for Laser, Atomic and Molecular Sciences, University of New Brunswick, Fredericton, New Brunswick E3B 5A3, Canada.
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Borneman TW, Cory DG. Bandwidth-limited control and ringdown suppression in high-Q resonators. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2012; 225:120-9. [PMID: 23165232 DOI: 10.1016/j.jmr.2012.10.011] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/11/2012] [Revised: 10/18/2012] [Accepted: 10/21/2012] [Indexed: 05/12/2023]
Abstract
We describe how the transient behavior of a tuned and matched resonator circuit and a ringdown suppression pulse may be integrated into an optimal control theory (OCT) pulse-design algorithm to derive control sequences with limited ringdown that perform a desired quantum operation in the presence of resonator distortions of the ideal waveform. Inclusion of ringdown suppression in numerical pulse optimizations significantly reduces spectrometer deadtime when using high quality factor (high-Q) resonators, leading to increased signal-to-noise ratio (SNR) and sensitivity of inductive measurements. To demonstrate the method, we experimentally measure the free-induction decay of an inhomogeneously broadened solid-state free radical spin system at high Q. The measurement is enabled by using a numerically optimized bandwidth-limited OCT pulse, including ringdown suppression, robust to variations in static and microwave field strengths. We also discuss the applications of pulse design in high-Q resonators to universal control of anisotropic-hyperfine coupled electron-nuclear spin systems via electron-only modulation even when the bandwidth of the resonator is significantly smaller than the hyperfine coupling strength. These results demonstrate how limitations imposed by linear response theory may be vastly exceeded when using a sufficiently accurate system model to optimize pulses of high complexity.
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Affiliation(s)
- Troy W Borneman
- Department of Nuclear Science and Engineering, Massachusetts Institute of Technology, Cambridge, MA, USA.
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Quine RW, Mitchell DG, Eaton GR. A General Purpose Q-Measuring Circuit Using Pulse Ring-Down. CONCEPTS IN MAGNETIC RESONANCE. PART B, MAGNETIC RESONANCE ENGINEERING 2011; 39B:43-46. [PMID: 21607115 PMCID: PMC3098457 DOI: 10.1002/cmr.b.20188] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/05/2023]
Abstract
A general purpose pulsed microwave circuit was developed for the purpose of measuring resonator Q by the pulse ring-down method in EPR spectrometers without pulse capability. The circuit was installed and tested in a Bruker X-band EPR bridge. This method and circuit could be adapted for use in a variety of spectrometers operating at various microwave frequencies.
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Affiliation(s)
- Richard W Quine
- School of Engineering and Computer Science, University of Denver, Denver, CO 80208
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Eaton SS, Eaton GR. Frequency Dependence of Pulsed EPR Experiments. CONCEPTS IN MAGNETIC RESONANCE. PART A, BRIDGING EDUCATION AND RESEARCH 2009; 34A:315. [PMID: 20148127 PMCID: PMC2818603 DOI: 10.1002/cmr.a.20148] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
The frequency dependence of the signal-to-noise ratio (S/N) that is theoretically possible for pulsed EPR experiments is the same as for continuous wave experiments. To select the optimum resonance frequency or frequencies for pulsed EPR experiments it is important to consider not only S/N, but also orientation selection, depth of spin echo modulation, and intensities of forbidden transitions. Evaluation of factors involved in selecting the optimum frequency for pulsed EPR measurements of distances between spins is discussed.
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Affiliation(s)
- Sandra S Eaton
- Department of Chemistry and Biochemistry, University of Denver, Denver, CO, USA 80208
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