The spin-lattice relaxation for a ¹⁴N NQR spin system is a dual exponential relaxation. Three measurement methods of spin-lattice relaxation times for a ¹⁴N NQR spin system are presented in this paper,the spin-lattice relaxation times T_1s and T₁₁ have been obtained by simulating experimental data with N-SIMPLEX method.Questions about the measurements of relaxation time for an NQR spin system in some concerned references have been put forward.

The excitation profile of BURP family pulses and Gaussian pulse cascades is simulated based on the Bloch equation. The selectivity of the various Dulses from these two kinds of pulses are compared systematically.The effect of inhomogeneity of the radiofrequency field B₁ on excitation profile is also simtilated. The pulses with optimum selectivity are suggested.

he propagator of a shaped pulse is taken as the rotation operator with the three Euler angles. The coherence evolutions under the shaped pulse are described by Multipole NMR, the tensor operator formalism, and the Cartesian operator formalism. The numerical calculation for a Gaussian-shaped pulse is made as an example.

Photosensitized reduction of oxygen to superoxide anion by cyanine dyes in dimethyl sulphoxide slaturatcd with oxygen has been studied by ESR. In aqueous solutions the hydroxide radical observed after irradiation originates from primarily formed O₂^·. The superoxide anion formation is due to photo-initiated electron transfer from the cyanine dyes to the dissolved oxygen. The intensity of ESR signals of the solutions containing various dyes used as photosensitizers is correlated with the redox potentials of dyes.

¹H and ¹³C NMR spectra of paraquileginine were studied using two-dimensional techniques. Based on the combination of 2D homo -heteronuclear NMR spectroscopy,all the ¹H and ¹³C NMR resonances were unambiguously determined.

The good relationships are presented which permit efficient calculation of the ¹³C-¹⁵N ¹³C -¹³N and ¹³C-¹⁹F nuclear spin-spin coupling constants. The method is applied with with the CNDO/2 molecular orbital approximation and natural hybrid orbitai scheme to a number of substituted hydrocarbons.Generally good agreement with the experimental data supports the idea that the hybridization and bond polarity,and the Fermi contact term are do minant factors in determining carbon-nitrogen and carbon-fluorine spin-spin coupling constants across one bond.This pennits us to interpret and calculate the ¹J_CN and ¹J_CF values based on he simple valence bond theory.

EPR dating is based on the detection of paramagnetic center created by natural radioactivity in a sample. The thermal stability of the paramagnetic center is related to the characteristics of the structure of the sample and the environmental temperature of sample site. We use mean life τ to express the thermal stability. Because the limit of EPR dating depends on the mean life, the research of thermal stability is an important part of fundamental researches for EPR dating. We studied thermal stability of diffrent paramagnetic centres of five samples by isothermal annealing experiments, and determined their mean life at 20℃,activation energy and frequency factor respectively.

The mechanism of the addition reactions Si-or P-centered radicals to diethyl 2-butenedioate has been studied by ESR method.Si-or P-centered radicals could be added to diethyl maleate which possesses cis-configuration.Hypertine splitting constants of the silyl radical adducts linked with different substituents were measured in our experiments. Radical polymerization of diethyl fumarate which possessetrans-configuration was initiated by radical Bu¹O·and produeed telomer or polymer. The addition reactions of Si-or P-centered radicals to diethyl fumarate could not happen due to steric hindranee.

The structure and stereochemistry of two plienolic compounds from aster tataricus were determined employing a variety of NMR experiments. Phase-sensitive COSY experiment was sunasfully used to resolve the crowded, strong coupled spin systems.The conformation of compound Ⅰ was discussed with the aid of molecular mechanism calculations.

One new compound was isolated form the EtOAc extract of CLYCYRRHIZA inflata bat collected at Gansu province in China.The structure was determined by ¹H、¹³C NMR、NOE different spectra,¹H-¹H COSY、¹³C-¹H COSY and ¹³C-¹H long-range COSY. It was named as Inflacoumarin A.

series of benzylated niannopyranosyl carboxylatea have been prepared and their NMR spectra have been investigated. At first, a pair of typical benzylated mannopymnose, 1-0-(3, 5-dinitro-benzoyl) -2, 3, 4, 6-tetra-0-benzyl-D-mannopponose liave been thoroughly studied by using NMR techniques. Three important results have been found:(1) PMR is more accumte and reliable than CMR in identifying the configuration of benzylated mannopyranosee; (2) The values of △δ_H-1 and ³J_H-1,2 are two main and good bases for the identification of theconfiguration; (3) The δ_C values of the two isomers (α and β) are in order of the following:C-1 > C-5 > C-3 > C-4 > C-2 > C-6.

A ³¹P in vivo NMR surface coil probe is presented which can be used for detecting the dynamic changes in tissue metabolism in living animals.The resonant frequency is 161.83 MHz and the unloaded Q is 300.The ³¹P NMR speetrum of brain、leg、musde、liver and brain in hypoxia of an intact mouse obtained with surface coil is presented,as examples.

To meet the requirement of NQR measurement of ¹⁴N compounds outside the probe-head, an NQR speetrometer with simplicity and economy was built. It utilizes the pulsed Fourier transform technique to apouire FID or echo signais for coherent accumulations. The whole system consists of two parts. The first part, hardware component, is made up of a radio-frcquency pulse gcnerator with power output of about 500 W, a probe-head, a receiver, an MCS-96 series single-chip micro-processor (8097BH) and an IBM pcrsonal computcr (PC/386). The second part includes softwam running in the single-chip micro-proessor and programs for the PC to handle numerical time-domain NQR data. With this apbectrometer, NQR signals from typical ¹⁴N samples of tens of grarns and within 10cm distance from the probe can be deteded in tens of seconds.