Elektronen-Kern-Doppelresonanz-Spektren von F-Zentren in Alkalihalogenid-Kristallen

(a), V. YA. ZEVIN (b), S. S. ISHCHENKO (a), N. P. BARAN (a), M. A. RUBAN (a), and V. V. TESLENKO (a) The hyperfine and quadrupole interactions of F-centres in NaCl were investigated by the ENDOR method. The constants of hyperfine interactions with nuclei of coordination shells I to X surrounding the vacancy have been determined. The quadrupole interaction with nuclei of shells 11, IV, VI, and VIII has been recorded and measured. General expressions for ENDOR frequencies are given in single-particle approximation, allowance being made for the deviation of the nuclear spin quantization axis from the direction of the constant magnetic field H , and for corrections due to second order perturbation theory. The angular dependence of ENDOR spectra has been investigated in detail and fully explained on the basis of theoretical formulae. The constants were determined at T = 20, 77, and 300 OK. 1nt.rodiictionThe I?-centres in NaCl were investigated by means of the electron nuclear The present work deals with a detailed investigation of magnetic hyperfine and quadrupole interactions of F-centres in NaC1. We discuss also the general expression for ENDOR frequencies in the single-particle approximation.

Section: Experiments and Discussion Of Resultssupporting

confidence: 75%

Section: Ntrodiictionmentioning

confidence: 99%

Magnetic Hyperfine and Quadrupole Interactions of F‐Centres in NaCl as Measured by ENDOR

Deigen

Zevin

Ischenko

et al. 1970

“…Details of the ENDOR method are explained elsewhere [9]. To first order one expects a desaturation of the E P R signal a t frequencies 1 h VENDOR = -(-gz Pr Bo + m~ w s h f ) 3 (1)…”

Section: E P R and Endor Measurementsmentioning

confidence: 99%

“…If the E P R lines are inhomogeneously broadened and saturable, as is the case for S-state transition metal ions in ionic crystals, much higher resolution of electron-nuclear spin interactions can be achieved by ENDOR (see Seidel [9]). With this method the superhyperfine (shf) interactions with the nearest neighbours can be determined to much higher precision (including the quadrupole interaction which is not resolved in EPR), and shf-and quadrupole interactions with many further out neighbours may be resolved.…”

Section: Introductionmentioning

confidence: 99%

ENDOR investigations of Cr⁺ centres in NaF, NaCl, and NaBr

Ziegler

1972

Isolated paramagnetic Cr+ centres in sodium halide crystals are studied by E P R and ENDOR. They show cubic symmetry. Superhyperfine and quadrupole interactions with many neighbouring ions (up to (300) in NaF) could be determined. The experimental results are interpreted in terms of two models for the wavefunction of the centre: overlap and covalency. A new way for the experimental determination of the coefficients for B-and x-covalency, using the isotropic superhyperfine interactions of neighbours (1 10) and (200), is proposed. The small anisotropic superhyperfine interaction of the nearest neighbours, which becomes even negative for Br-in NaBr, cannot be understood along these lines.Isolierte paramagnetische Cr+-Zentren in Natriumhalogenideinkristallen wurde mit ESR und ENDOR untersucht. Sie zeigen kubische Symmetrie. Superhyperfein-und Quadrupolwechselwirliungen mit zahlreichen Nachbarkernen (bis zum Kern (300) in NaF) konnten bestimmt werden. Die experimentellen Ergebnisse werden anhand von zwei Modellen fur die Zentrenwellenfunktion diskutiert : tfberlappung und Kovalenz. Daraus ergibt sich eine neue Methode zur experimentellen Bestimmung der Koeffizienten von B-und x-Kovalenz, indem man die isotropen Superhyperfeinwechselwirkungen der Nachbarn (1 10) und (200) heranzieht. Die kleine anisotrope Superhyperfeinwechselwirkung mit den nachsten Nachbarn, die fur Br-in NaBr sogar negativ wird, kann auf diese Weise nicht erklart werden.

“…The method of electron nuclear double resonance (ENDOR) has turned out to be a powerful tool for the determination of these interactions which cannot be resolved by ESR. It is essentially a nuclear magnetic resonance of the nuclei coupled to the paramagnetic centre, using the desaturation of the simultaneously observed ESR signal for its detection [2,3,41. The method was invented by Feher [5] and soon applied to the F-centre in KC1 by him [6].…”

Section: Introductionmentioning

confidence: 99%

Hyperfine and Quadrupole Interactions of the F‐Centre in KCl as Measured by ENDOR

Kersten

1968

in KC1 as Measured by ENDOR BY R. KERSTENThe isotropic and anisotropic hyperfine constants of the nuclei surrounding the F-centre in KC1 were newly determined by electron nuclear double resonance (ENDOR) in a region within the distance of three lattice constants around the centre (up to nuclei 003). Quadrupole interactions of nuclei 002, 102, and 112 could be measured.Die isotropen und anisotropen Hyperfein-Konstanten der Kerne in der Umgebung des F-Zentrums in KCl wurden mit Elektronen-Kern-Doppel-Resonanz (ENDOR) in einem Bereich von drei Gitterkonstanten um das Zentrum (bis zu Kernen 003) erneut beatimmt. Quadrupol-Wechselwirkungen fiir die Kerne 002, 102 und 112 konnten gemessen werden. IntroductionThe F-centre in KC1 has an absorption line in electron spin resonance (ESR) which is inhomogeneously broadened by the magnetic coupling to the surrounding lattice nuclei, the main contribution to the line width arising from the six nearest neighbour potassium nuclei (shell 1)l) [l]. The method of electron nuclear double resonance (ENDOR) has turned out to be a powerful tool for the determination of these interactions which cannot be resolved by ESR. It is essentially a nuclear magnetic resonance of the nuclei coupled to the paramagnetic centre, using the desaturation of the simultaneously observed ESR signal for its detection [2, 3, 41. The method was invented by Feher