SU1476362A1 - Method of generating electron paramagnetic resonace tomogram - Google Patents

Abstract

This invention relates to the field of magnetic introscopy, specifically to electron paramagnetic resonance imaging. The method can be used to study and control the internal structure of a substance, in particular, to determine the volume distribution function of paramagnetic centers in a sample and the nature of the interaction between them without destroying it. The goal is to improve the accuracy and reliability of the construction of the tomogram. The sample placed in an alternating magnetic field, impose a constant magnetic field, measure the values of the left and right peaks of the first derivative of the EPR signal and the distance between them, determine the scale parameter and scale points of the EPR signal, measure it at scale points of the intensity of the EPR signal and determine the moments of the EPR signal, impose an additional gradient field, measure the left and right peaks of the first derivative of the EPR signal, measure the distance between them, determine the scale parameter and scale points of the EPR signal, measure At scaling points, the intensity of the EPR signal is measured and the moments of the EPR signal are determined, the orientation of the sample is changed at least twice, the times of the EPR signal are determined every time and the EPR image is calculated based on the signal moments. 1 il.

Description

one

The invention relates to magnetic introscopy, specifically to electron paramagnetic resonance imaging, and can be used to study and control the internal structure of a substance, in particular, to determine the volume distribution function of paramagnetic particles in a sample and the nature of the interaction between them without destroying it.

The purpose of the invention is to improve the accuracy and reliability of the construction of the tomogram.

The drawing shows the EPR signals of the absorption of natural diamond without tradition-U

O5 SO O Yu

ent magnetic field (curve 1) and with a magnetic field gradient (curve 2).

The method for constructing EPR tomograms is illustrated on a specific sample, a natural diamond. The structure of the diamond under investigation is saturated with defects responsible for the EPR signal. The density of defects varies in volume from point to point, therefore, the EPR signals from small sample volumes located at a distance from each other differ in their parameters (intensity, width, shape) depending on a given amount of magnetic particles in a given the volume and nature of the interaction between them (dipole-dipole, exchange interaction, dispersion, saturation, etc.). Because of this, the resulting EPR signal is a certain integral characteristic that reflects the unequal density of magnetic particles in the sample volume, and its shape is different from the ideal form of Lorentz or Gauss. It is this EPR signal from natural diamond that was obtained by imposing on

sample of alternating and constant magnetic fields and shown in the drawing (curve 1). To measure the moments, the maximum values of the left and right peaks of the first derivative of this signal are determined. In accordance with the expressions for the Lorentz y1 form factor, and the Gauss form factor:

ten

i -2X + a (M-X) y (M + X2) 2

M-Ј i2 -2X 1p2 +. (1-2Х21п2) + 06 (M-1)

Y /

rM (+ 1)

where a

dispersion parameter;

saturation;

u f

dimensionless parameter:

  - parameter

H-H0

1/2 th

The dispersion parameter a and the position of the maximum values of the left XL and right XR peaks of the first derivative are measured. Limit the required interval X, 2 experimental EPR signal. At integer scaling points of a limited interval, the intensity of the EPR signal is measured. Based on the analytical expressions for the moments of the /-element in the interval,, +.

-x2 + w2-a,

h

 - 1G + 13zo.

#

4, ,, Е11.

W5-b

/ #

11/6 L

H 29 X6 + EZ

W7-b

,

W6-70 W -a,

-X7

// 55 X8 + 61

48

Ws- 126

-X9

e W-scale parameter

parameters a and b

left half space ():

.y o-y W ();

but

L.1 + 1-X,

(Xi + l) (); right half space ():

Yl (X,) (Xl + t)

, -Xi.

Mr

- ();

b y Xt} -a-Xt,

The moments of the / -element are determined and the moments of the experimental EPR signal, whose shape differs from the ideal Lorentz (Gaussian) shape, are measured by their summation.

The resulting moment for the signal with the "non-ideal Lorentz form factor is written as a sum

i

If necessary, on the same interval and on the same scale, the moments of the EPR signal with the ideal Lorentz shape (in the drawing of curve 2) are determined. A gradient magnetic field is imposed. Already described method for a broadened gradient magnetic field of an experimental EPR signal, the dispersion parameter a is determined, the scale broadened parameter WQ. and at the same integer scale points

of the broadened interval X, X, the moments are measured using the analytical expressions given. In this case, the correction is carried out, which consists in the fact that in the process of measurement in analytical expressions

0 replace the scale parameter W with the broader scale parameter H & . Further, in the construction of EPR tomograms, such operations are performed as they usually do (they change the constant magnetic field by a small amount, shifting the resonance plane,

5 rotate the sample, etc.), each time measuring the moments of the EPR signal in the manner described and based on the numerical values of the moments, taking into account the analysis of the interaction between particles, dispersion and absorption, an EPR scan is generated.

0

Claims (1)

Invention Formula The method of constructing an EPR tomogram, which consists in imposing a constant and a gradient magnetic field on a sample obstructed in an alternating magnetic field, measures the intensity of the EPR signal, changes the orientation of the sample, measuring each time the intensity of the EPR signal, and on the basis of this, an ESR tomogram is constructed, characterized in that, in order to increase the accuracy and reliability of tomogram construction, in a sample placed in an alternating and constant magnetic field, the EPR signal is measured, the values of the left and right peaks are measured. the first derivative of the signal and the distance between them, determine the scale parameter and the scale points of the signal, measure the scale points of the signal intensity and determine the moments of the EPR signal, impose to a constant gradient magnetic field, record the EPR signal, measure the left and right peaks of the first derivative of the signal, measure the distance between them, determine the scale parameter and signal scale points, measure the signal intensity at scale points , the orientation of the sample is changed at least twice, the moments of the EPR signal are determined each time, and an ESR tomogram is generated based on the signal moments.