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Perturbed Angular Correlations of γ-rays (PAC) Spectroscopy

  1. Lars Hemmingsen1,
  2. Tilman Butz2

Published Online: 15 MAR 2008

DOI: 10.1002/0470862106.ia322

Encyclopedia of Inorganic Chemistry

Encyclopedia of Inorganic Chemistry

How to Cite

Hemmingsen, L. and Butz, T. 2008. Perturbed Angular Correlations of γ-rays (PAC) Spectroscopy. Encyclopedia of Inorganic Chemistry. .

Author Information

  1. 1

    University of Copenhagen, Frederiksberg, Denmark

  2. 2

    University of Leipzig, Leipzig, Germany

Publication History

  1. Published Online: 15 MAR 2008


In this article, we give an elementary introduction to the theory and applications of perturbed angular correlation of γ-rays (PAC) spectroscopy. In most applications in bioinorganic and inorganic chemistry the nuclear quadrupole interaction (NQI) is measured, providing a spectroscopic fingerprint of the local electronic and molecular structure and dynamics at the PAC probe site. The focus is on selected illustrative applications of PAC spectroscopy in bioinorganic chemistry: (i) local structure at metal ion binding sites in the bacterial mercury sensor MerR; de novo designed proteins; alcohol dehydrogenase–pH dependence; carboxypeptidase A—crystalline state versus solution; and carboxypeptidase A–during the hydrolysis of substrate; (ii) trapping intermediates in reactions using rapid freeze quenching; (iii) in vivo experiments on Cd(II) binding to biomolecules in cyanobacteria; (iv) cooperativity of metal ion binding in multinuclear sites; (v) dynamics of protein folding; (vi) rotational diffusion of biomolecules as a tool to monitor protein–protein interactions; (vii) exchange dynamics; and (viii) internal dynamics in proteins.

Examples from inorganic chemistry and solid state physics are included for cases where the information derived is different from that already presented in the examples from bioinorganic chemistry: (i) magnetic properties of metals; (ii) defects trapped by the impurity PAC probe atom; (iii) temperature and pressure dependence of the EFG in metals; (iv) amorphous metals, alloys and internal oxidation; (v) metal surfaces and interfaces; (vi) semiconductors; (vii) phase transitions; (viii) charge density waves in transition metal dichalcogenides; (ix) intercalation reactions in 2H-TaS2; (x) structure and bonding; (xi) single crystal experiments.


  • PAC;
  • TDPAC;
  • NQI;
  • EFG;
  • coordination geometry;
  • structure;
  • dynamics;
  • metal ion containing proteins;
  • protein–protein interactions;
  • metals;
  • alloys;
  • insulators