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2000 (1)
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1Author    Nicolai Sinyavsky, Michal Ostafin, Mariusz MaćkowiakRequires cookie*
 Title    Rapid Measurement of Nutation NQR Spectra in Powders Using an RF Pulse Train  
 Abstract    The method of two-dimensional nutation NQR spectroscopy, introduced by Harbison in 1989, has been successfully used for determining of the asymmetry parameter of the EFG tensor for spin-3/2 nuclei in both powdered and monocrystal samples in the absence of an external magnetic field. The inconvenience inherent in the method, however, is the long time required, because data acquisition must be repeated for various RF pulse lengths. We discuss a method to reduce the time of the nutation experiment by using a sequence of identical short RF pulses of length r w and distance t. It is shown that for an NQR frequency co 0 , frequency offset Aco, and pulse parameters satisfying the relation co 0 1 -I-Aco t w = 2 n k (k = 1, 2, 3,..., n) a synchronism of pulse action takes place and the nutation interferogram can be measured "stroboscopically" between the pulses. The maximum time saving factor that can be obtained as compared to the conventional nutation experiment is of the order of the number of pulses used in a pulse train. The method has been successfully applied for determination of the asymmetry parameter for one of the two 35 C1 sites in polycrystalline 2,4,6-trichloro-l,3,5-triazine (cyanuric chloride). 
  Reference    Z. Naturforsch. 51a, 363—367 (1996); received February 13 1996 
  Published    1996 
  Keywords    Nuclear quadrupole resonance, Two-dimensional nutation spectroscopy, Asymmetry parameter 
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 TEI-XML for    default:Reihe_A/51/ZNA-1996-51a-0363.pdf 
 Identifier    ZNA-1996-51a-0363 
 Volume    51 
2Author    David Stephenson, JohnA S Smith, St Augustine, Tobago TrinidadRequires cookie*
 Title    Double Resonance Detection Using Zero Field Level Crossing  
 Abstract    Double resonance level crossing detection cannot normally be used to record transitions between the quadrupole Zeeman levels. Neither can it be used if the quadrupole resonance frequency is larger than the proton NMR frequency in high field. A simple variation of the level crossing experiment is demonstrated which allows energy to be efficiently transferred from quadrupole to proton system and hence lead to detection in these two cases. In the case of the quadrupole Zeeman levels it allows transitions between the ±\ levels to be detected in a small magnetic field, allowing measurement of the asymmetry parameter (r\) for spin 3/2 systems. This is demonstrated for the 1X B nucleus in triethanolamine borate. Detection of high frequency quadrupole transitions is demonstrated from which relaxation information is obtained. 
  Reference    Z. Naturforsch. 53a, 301—304 (1998); received October 31 1997 
  Published    1998 
  Keywords    NQR, Asymmetry Parameter, Relaxation, n B, 35 C1 
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 TEI-XML for    default:Reihe_A/53/ZNA-1998-53a-0301.pdf 
 Identifier    ZNA-1998-53a-0301 
 Volume    53 
3Author    ValentinP. Feshin, ElenaV. FeshinaRequires cookie*
 Title    Correlation between the 35 CI NQR Parameters of Chloro-containing Organic and Organometallic Compounds and the Results of ab initio Calculations  
 Abstract    The results of comparison of experimental 35 C1 NQR parameters for a great number of organic and organometallic compounds and estimated ones using ab initio calculations at the RHF/6-31G(d) level were systematized. The NQR frequency changes on going from one compound to another depend, in general, on the changes of populations of the CI atom p"-orbitals in these compounds and, first of all, of populations of their less diffuse parts. 
  Reference    Z. Naturforsch. 55a, 555—559 (2000); received December 15 1999 
  Published    2000 
  Keywords    ab initio Calculations, p-orbital Populations, 35 C1 NQR Frequency, Asymmetry Parameter, Chloro-containing Organic and Organometallic Compounds 
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 TEI-XML for    default:Reihe_A/55/ZNA-2000-55a-0555.pdf 
 Identifier    ZNA-2000-55a-0555 
 Volume    55