Nuclear quadrupole resonance NQR spectroscopy

G. P. Wulfsberg, Nuclear Quadrupole Resonance (NQR) Spectroscopy, in Encyclopedia of Inorganic Chemistry, 2nd edn, (R. B. King ed.), John Wiley Sons, Ltd., Chichester, UK, 2008. 

With the help of 35C1 Nuclear Quadrupole Resonance (NQR) spectroscopy and AMI, MNDO h PM3 calculation data of tautomers of 2-trichloromethyl-5(6)-nitrobenzimidazole it is established that 5-nitro tautomer is more preferable than its 6-isomer (Scheme 3.76) [1407],... 

Magnetic Circular Dichroism (MCD) Spectroscopy Nuclear Magnetic Resonance (NMR) Spectroscopy of Metallobiomolecules Nuclear Quadrupole Resonance (NQR) Spectroscopy Electron Spin Echo Envelope Modulation (ESEEM) Spectroscopy. 

Of the NMR-active nuclei around three-quarters have / > 1 so that the quadrupole interaction can affect their spectra. The quadrupole inter action can be significant relative to the Zeeman splitting. The splitting of the energy levels by the quadrupole interaction alone gives rise to pure nuclear quadrupole resonance (NQR) spectroscopy. This chapter will only deal with the case when the quadrupole interaction can be regarded as simply a perturbation of the Zeeman levels. 

This chapter takes a critical look at new publications relating to pure nuclear quadrupole resonance (NQR) spectroscopy for inorganic and organometallic species, up to the end of 2011. 

Nuclei that have a nuclear electric quadrupole moment have energy levels that arc split in the presence of an electric field gradient. Such a gradient does not have to be applied externally, but is a molecular property, and is almost always non-zero, the exceptions being in perfectly octahedral or tetrahedral environments. Transitions between these energy levels are observed in nuclear quadrupole resonance (NQR) spectroscopy, described in the on-line supplement for Chapter 4 on NQR. 

In so-called pure nuclear quadrupole resonance (NQR) spectroscopy, the magnetic dipole transitions between the levels of (18.51) satisfy the selection rule Am = 1. For spin i there are two transitions, = 3eQVzzl20h and P2 = 2vi when T) = 0. For spin I, = eQVzJ 4h and = 2pi, ps = 3pi when t = 0. In these cases both the coupling constant, eQVzz, and asymmetry parameter may be determined from frequency measurements alone. 

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