Zeeman NQR Studies on Polycrystals of Copper Compounds, Arsenic Compounds, and Chlorine Compounds

Abstract

Powder Zeeman NQR (PZNQR) spectra of 63Cu,75As, and 35Cl in various compounds have been observed at 77 K. On the basis of the types of simulated integral curves of PZNQR absorption, the estimated asymmetry parameters of the electric field gradients have been divided into three classes; (1) measurable, (2) small (smaller than about 0.05), and (3) very small (probably zero). The asymmetry parameters have been found to be very small ( Cu, NQR frequency = 26.704 MHz) in Cu,0;0.40 (63Cu, 32.617 MHz) in KCu(CN)2; very small (75As, 116.820 MHz) in As2O3 ; very small (75As, 78.950 ; 35Cl, 25.0567 and 25.4036 MHz) and small ( 35Cl, 24.9581 MHz) in ASCl3 ; very small (75As, 98.501 and 99.046 MHz) in As(C6H5)3; small (38.389 MHz), 0.15 (38.464 MHz), and 0.14 ( 38.503 MHz) for 35Cl in hexachlorobenzene; small ( 35.847 MHz) and very small ( 39.154,39.603 , and 39.615 MHz) for 35Cl in l-chloro-2-(trichloromethyl)-benzene; small ( 32.619 MHz) and very small ( 32.878 MHz) for 35Cl in 1,4-dichlorobutane; very small ( 37.828 and 38.051 MHz) for 35Cl in 1,1,1 -trichloroethane.

Powder Zeeman NQR Study on the Absorption Forms for Nuclear Spin 5/2

“…However, the PZNQR methods based on the detection in a differential form sometimes led to noticeable errors in estimating 77 values, compared to the method using SZNQR. We have observed the PZNQR spectra in simple integral forms using a bridge circuit and obtained the 77 values for sever- al nuclei with spin 3/2, which are in good agreement with those evaluated from SZNQR [10][11][12][13][14], In this paper we report an experimental and simulation study on PZNQR for nuclear spin 5/2. Although 77 values are approximately obtained only from the frequencies of two NQR lines for nuclear spin 5/2, it is obvious that the PZNQR method is another useful way to estimate small 77 values.…”

“…1 and 2, the abscissa and ordinate of each curve represent a reduced frequency and an absorption intensity, respectively. When the angle between Hr and Ho is 0° or relatively small, the shapes of the curves drastically change as 77 increases, in the following manner, (i) When an 77 value is very small (type 1; 77 = 0), the line shape exhibits two shoulders like the style of the American football player, (ii) While an 77 value is small (type 2; 0< 77 < around 0.01) but not zero, the line shape has two small peaks which are symmetrically located on the shoulders, as seen in the case of the small 77 type for a nuclear spin of 3/2 [ 13]. (iii) When an 77 value is not small (type 3; around 0.01< 77), the line shape has two symmetrical dips in stead of the peaks, as also seen in the case of not small 77 type for a spin of 3/2.…”

Spin–Spin Coupling between Quadrupolar Nuclei in Solids: 11B–75As Spin Pairs in Lewis Acid–Base Adducts

“…Table provides a list of 75 As and 11 B NMR properties relevant to this study. Arsenic-75 has a moderate nuclear electric quadrupole moment and a fairly large Sternheimer antishielding factor (γ ∞ = −7.09) which leads to generally large nuclear quadrupolar coupling constants (e.g., values on the order of 100 MHz or larger are common). − The muonic Q ( 75 As) = 30.0(50) fm 2 currently recommended by IUPAC is believed to be less precise than Q ( 75 As) = 31.1(2) fm 2 , recently determined from microwave spectroscopic data for AsP and coupled-cluster calculations performed at the CCSD­(T) level of theory . The latter value will therefore be used in this work.…”

“…In 75 As NMR studies of liquids, large C Q ( 75 As) values lead to extremely efficient quadrupolar relaxation and broadening, limiting studies to 75 As nuclei at tetrahedral or octahedral sites since C Q ≈ 0 in those cases. Relatively few examples of 75 As NMR spectra of nonmetallic solids are documented in the NMR literature. ,− In solids, C Q ( 75 As) values are mostly known from nuclear quadrupole resonance (NQR) − and microwave spectroscopy experiments. − Note that information obtained from 75 As NQR studies of nonsymmetric molecules in powdered samples is limited, as C Q ( 75 As) and the quadrupolar asymmetry parameter, η­( 75 As), are difficult to determine independently from experiment due to 75 As possessing a nuclear spin number of I = 3/2, giving the nucleus only one NQR transition ( m I = ± 1/2 ↔ m I = ± 3/2) dependent on both parameters in zero-field conditions . There are, however, techniques available to get around this limitation .…”