K3CrO8 in K3NbO8 as a Proposed Standard for g-Factor, Spin Concentration, and Field Calibration in High-Field EPR Spectroscopy
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- 作者：Brant Cage ; April Weekley ; Louis-Claude Brunel ; and Naresh S. Dalal
- 刊名：Analytical Chemistry
- 出版年：1999
- 出版时间：May 15, 1999
- 年：1999
- 卷：71
- 期：10
- 页码：1951 - 1957
- 全文大小：85K
- 年卷期：v.71,no.10(May 15, 1999)
- ISSN：1520-6882
文摘
Currently there is a lack of an internal standard for EPRspectroscopy employing magnetic fields higher than about3 T. It is here suggested that the solid solution of 0.5%K3CrO8 into K3NbO8 fulfills many of the requirements ofsuch a standard. Its main EPR signal is due to a 3d1electron and consists of a single sharp peak for single-crystal samples. The peak width ranges from 1.5 G (0.15mT) at the X-band (Bo = 0.34 T) to 4 G (0.4 mT) at 330GHz (Bo = 11.8 T). The g-values have been determinedas g
= 1.98508 ± 0.00005 and g
= 1.94272 ±0.00005. This high degree of precision is necessarybecause EPR work at high frequencies can resolve g-tensors to six or seven significant figures. Additionally,K3CrO8 in K3NbO8 provides a field calibration standardvia a weak but well-resolved hyperfine structure from its53Cr isotope (I = 3/2, natural abundance 9.5%): A =39.55 ± 0.08 G, A = 11.49 ± 0.05 G. Variable-temperature and variable-frequency studies demonstratethat this sample can serve as a reliable standard for EPRmeasurements over the range of at least 5-300 K and9-330 GHz. The sample can be prepared in a simple,reproducible way and can serve also as a standard forabsolute spin count, thus making it unique among theother standards in current usage.
= 1.98508 ± 0.00005 and g = 1.94272 ±0.00005. This high degree of precision is necessarybecause EPR work at high frequencies can resolve g-tensors to six or seven significant figures. Additionally,K3CrO8 in K3NbO8 provides a field calibration standardvia a weak but well-resolved hyperfine structure from its53Cr isotope (I = 3/2, natural abundance 9.5%): A =39.55 ± 0.08 G, A = 11.49 ± 0.05 G. Variable-temperature and variable-frequency studies demonstratethat this sample can serve as a reliable standard for EPRmeasurements over the range of at least 5-300 K and9-330 GHz. The sample can be prepared in a simple,reproducible way and can serve also as a standard forabsolute spin count, thus making it unique among theother standards in current usage.