SU968719A1 - Method of measuring interaction parameters between paramagnetic centers - Google Patents

Description

(54) SPECIAL MEASUREMENT OF INTERACTION PARAMETERS BETWEEN PARAMAGNETIC CENTERS

one

The invention relates to the measurement of interaction parameters between paramagnetic centers by radospectroscopic methods and can be used in various structural physics of chemical research.

A known method for measuring the interaction between paramagnetic centers using double electron resonance C

However, this method does not provide the possibility of a smooth and tightly controlled frequency tuning of radio frequency generators.

The closest to the proposed method is the measurement of interaction parameters between the paramagnetic center of a gas, including placing a sample in a polarizing magnetic field and generating a spin echo signal from two groups of paramagnetic centers, causing the first group of paramagnetic centers to be excited by acting on a sample of radio frequency pulses, and to excite the second group of paramagnetic centers, an additional radio frequency pulse is used, supplied in one of the Alov sequence of radio frequency pulses With 2.

However, to implement the known method, a bimodal resonator is necessary, both modes of which are tuned to the Zeeman frequencies of both groups.

10 paramagnetic centers, the interaction of which is studied, as well as two separate radio frequency generators at these frequencies. In addition, it is necessary to ensure that the possibility of a smooth and

ts of a strictly controlled frequency tuning of one of the oscillators relative to the other in the mode of oscillations of the resonator associated with this generator. Meeting these requirements at the present time

20 often encounters significant technical difficulties.

Claims (2)

The aim of the invention is to improve the measurement accuracy by simplifying the excitation system of the paramagnetic centers. This goal is achieved in that, according to the method of intending the interaction parameters between paramagnetic centers, including placing the sample in a transient magnetic field and generating a spin echo signal from two groups of paramagnetic centers, the excitation of the first group of paramagnetic centers is accomplished by exposing the sample to a sequence of radio frequency pulses , and for the excitation of the second group of paramagnetic centers, an additional radio frequency pulse is used, which is fed in one of the inter alota radio frequency sequence; astrotic pulses, an additional radio frequency pulse is fed at a fixed carrier, a frequency equal to the carrier frequency of the sequence for frequency pulses, and the polarizing magnetic field in the sample is changed to the value at which the Zeeman frequency of the second group of paramagnetic centers becomes equal to the carrier frequency of the radio frequency pulse train. Technically, this can be done, for example, by modulating the polarizing magnetic field at the location of the sample with rectangular pulses that coincide in time and duration with an additional RF pulse, and the amplitude and polarity of the modulating pulse of the polarizing magnetic field must be set to TaioiMH so that The Zeeman frequency of the second group of paramagnetic centers in the resultant polarizing magnetic field was equal to the carrier frequency of the sequence of radio-frequency pulses. To implement the proposed method, a conventional single-mode resonator is used, and one generator of radio-frequency pulses operating at a fixed frequency. Reconstruction of the Frequently Frequency Frequency of the second group of paramagnetic centers excited by an additional radio frequency pulse is made by a simple change in amplitude of the modulus of the polarizing magnetic field pulse. The drawing shows graphs explaining the principle of the method. In the coordinates 0 –M o, the hypothetical spectrum of the electron-paramagnetic resonance with the splitting of the DNO between the PIDIs 1-3, belonging to various interacting paramagnetic centers, is given. The spin echo signal is observed due to the excitation of line 1. The coordinates of the RRC-t show the change in radio frequency modality in the cavity in time. Pulses 4 are stimulating pulses of a sequence of radio frequency pulses with an interval T between them. At interval T after the second excitation pulse, a spin echo signal 5 appears from the sequence of RF pulses. An additional radio frequency pulse 6 is applied within the second TG interval after the second excitation pulse of the radio frequency pulse sequence. In the coordinates HQ - –b, the variation of the momentum of the magnetic field in time is shown. During the operation of the radio frequency pulse sequence and the observation of the spin echo signal, the magnitude of the polarizing magnetic field is constant and equal to Er, where the Zeeman frequency of line I of the triplet is equal to WQ-TCHIolGDE T-1 - the effective gyromagnetic ratio of the first group of paramagnetic centers and the frequency of the sequence of radio frequency pulses . The modulating pulse 7 with the amplitude of IOo coincides in time with the additional radio-frequency pulse and overlaps it somewhat. The pulse amplitude is determined from the condition of Noz-dC-; where is the effective gyromagnetic ratio of the second group of paramagnetic centers. An approximate change in the spin-echo signal depending on the amplitude of the modulating pulse is shown in U (.- & H) coordinates. If the amplitude of the model pulse of the LI or II pulse is equal, lines 2 or 3 are excited and, as a result, the amplitude of the spin echo changes. The technical effect of the proposed This method is technical and is determined by measuring the accuracy of measurement of the parameters of interaction between paramagnetic centers, which expands the possibilities of studying the physicochemical processes in a substance. This method allows us to extract new additional information about various substances, the receipt of which is either impossible or fraught with significant difficulties 59 Claims of the invention A method for measuring interaction parameters between paramagnetic centers involving placement of a sample into a negative magnetic field and formation of a spin echo signal from two groups of paramagnetic centers, the first group of paramagnetic centers being excited by acting on a sample of a sequence of radio frequency mpulsov, and to drive the second group of paramagnetic centers used additional RF pulse supplied in one of the slots of radio frequency pulse sequences and otlichayush and in that, in order to increase measurement accuracy by simplifying the driving system paramagnetic cent An additional RF pulse is applied at a fixed frequency equal to the frequency of the RF pulse sequence, and for the duration of the additional pulse the polarized magnetic field in the sample is changed to the value at which the Zeeman frequency of the second group of paramagnetic centers becomes equal to the frequency radio frequency pulse sequences. Sources of information taken into account in the examination 1. Verc J., Bolton J. Theory and practice of applying the EPR method. M., Matthew, 1975, p. 406. 2. USSR author's certificate number 741135, cl. GO1 N 24 / 1Q, 1980 (prototype).