Nuclear quadrupole resonances due to 121Sb, 123Sb, Cl35, and 37Cl have been observed in SbCl5POCl3, SbCl5CH3CN, and SbCl5 at a number of temperatures. The resonances in SbCl5POCl3 are correlated with the known structure of that complex. A covalent structure for the SbCl5CH3CN complex is proposed on the basis of its resonances. A phase change in SbCl5 occurs between 195° and 210°K. At 210°K and above the Sb resonances are consistent with a trigonal bipyramidal structure and the chlorine resonances are not visible. At 195°K and below the resonances of Sb and Cl indicate a complex structure. A bridged dimeric structure similar to that in NbCl5 is suggested. A discussion of relative intensity measurements is included. A qualitative discussion of the temperature dependences and their implications on the molecular dynamics of these molecules is also included.

Chlorine and Antimony Nuclear Quadrupole Resonance in SbCl5CH3CN, SbCl5POCl3, and SbCl5

A super-regenerative spectrometer has been constructed which possesses effective sideband suppression together with automatic gain control and direct frequency calibration of the recorder chart. An analysis of the super-regenerative circuit shows that the gain of the circuit depends mainly on the length of the damping period; consequently, by making the damping period independent of quench frequency, relatively little gain change occurs when the latter is varied in order to suppress the sidebands. The gain may therefore be simultaneously controlled by changing the damping period and damping efficiency by a feedback loop which maintains constant noise output. Frequency measurements are greatly simplified by providing circuitry which operates a separate marker pen on the recorder chart whenever the spectrometer frequency zero-beats with a set of harmonics from a standard frequency source. A small delay in the marker channel then ensures that sideband zero-beats are not printed when sideband suppression is in use; otherwise, the quench frequency is made a small multiple or sub-multiple of the quench frequency. As an example of the applications of the new instrument part of the 35Cl spectrum of PCl5 at 77°K is shown, with direct calibration of the frequency scale; signals are clearly resolved which have been missed by previous workers.

https://iopscience.iop.org/article/10.1088/0022-3735/1/1/302/pdf

An improved super-regenerative spectrometer for nuclear quadrupole resonance spectroscopy

Nuclear quadrupole coupling in organotin chlorides. II. Dichlorides

Triarylphosphite substitution in pentakis(aromatic isocyanide)cobalt(I)

We have studied nitrogen and chlorine pure quadrupole resonance spectra in some charge transfer complexes with a chloroform molecule as acceptor, the donors being some amino and heterocyclic compounds. A discussion of the present results and consideration of previous data confirm the charge transfer in these complexes. From the observed frequency shifts with respect to the uncomplexed compounds, the charge transfer can be estimated to a few per cent of an electron charge. Nous avons etudie la resonance quadripolaire pure de l'azote et du chlore dans quelques complexes a transfert de charge. L'accepteur y est le chloroforme, tandis que les donneurs y sont des amines ou des heterocycles. La discussion des resultats obtenus, compte tenu de donnees anterieures, semble confirmer le transfert de charge dans ces complexes. L'estimation du transfert, a partir des deplacements de frequence mesures, fournit une valeur egale a quelques centiemes de la charge electronique.

Observation de la résonance quadripolaire pure de l'azote et du chlore dans quelques complexes à transfert de charge

A description is given of a wideband feedback coherence control system for superregenerative NQR spectrometers. By making use of a servo motor to adjust the oscillator grid bias, increases in rf searching band are possible. As an example, a bandwidth of 30 Mc around a center frequency of 70 Mc has been obtained. The sensitivity of the circuit to nuclear quadrupole resonance signals is high. The spectrometer will operate unattended.

G. E. Peterson

Papers

Wideband Feedback Coherence Control for Superregenerative NQR Spectrometers