JPS5952779B2 - electron spin resonance device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a device for reducing measurement errors in an electrolytic spin measurement device.

An electron spin resonance apparatus (ESR) is an apparatus for determining the physical properties of a sample material by utilizing the magnetic properties of unpaired electrons present in the sample material, and its configuration is schematically shown in FIG.

In FIG. 1, reference numeral 1 denotes a cavity resonator into which a sample 2 is inserted, and is installed within the gap between the magnetic members 4 in order to apply a strong static magnetic field to the sample. A central control circuit (CPU) 6 serves as an excitation power source for the coil 5 wound around the member 4.
A sweep signal generator 7 controlled by the oscilloscope is used to provide a relatively slowly varying static magnetic field to the sample material. This static magnetic field causes separation of electron spin energy levels in the sample material due to the Zeeman effect, and a phenomenon occurs in which the microwave power supplied from the microwave generator 8 to the cavity 1 via the magic T9 is absorbed. Absorption of microwave power in the sample in the cavity 1 upsets the power balance in the magic T, and this variation is detected by the microwave detector 10. In order to extract this detection signal as an AC signal rather than a DC signal, an AC modulated magnetic field is superimposed on the sweeping static magnetic field applied to the sample, and the modulation frequency suppresses the l/f noise of the microwave detector 10. Therefore, it is set to 100KH2 or more. In order to efficiently apply such a high-frequency modulated magnetic field to the sample, a magnetic field modulation coil 11 is installed inside the cavity 1, and a high-frequency oscillator 12 sends 100 KH to the coil. The above high frequency current is supplied. The microwave modulated by the high frequency magnetic field in this manner is detected by the microwave detector 10, and then further detected by the phase detector 13 to which the reference signal from the high frequency oscillator 12 is supplied. The phase component is detected and applied together with the output signal of the sweep signal generator 7 to the central control circuit 6 and the display device 14 for recording and recording.
Display is performed. In order to perform measurements using such an electron spin resonance device with high precision, the Q value of the cavity in which the sample is placed must be constant, but inserting the measurement sample into the cavity itself changes the Q value of the cavity. Therefore, for high-precision measurements, it is necessary to consider detection errors due to sample insertion.

The present invention aims to automatically correct such detection errors. FIG. 2 is a schematic diagram showing the cavity used in the present invention, and 15 in the figure is the cavity 1.
shows a waveguide that guides the microwaves supplied from Magic-T.

A very small amount of a standard (comparison) sample 17 is attached to a glass tube 16 in the cavity 1, and the Q value of the cavity depending on the presence or absence of the sample can be almost ignored. On the other hand, the measurement sample 2 is inserted into the cavity through the sample insertion glass tube 18, but since the amount of measurement sample 2 is usually larger than the amount of the standard sample 17, it causes a slight change in the Q value of the cavity. Since the intensity of the measured spectrum is approximately proportional to the Q value of the cavity, the Q value of the cavity changes each time a different sample is inserted, making comparisons of spectral intensities between different samples inaccurate. There were flaws.
In the present invention, first, the measured spectrum of only the standard sample 17 before the Q value of the cavity changes is stored,
Next, the measurement sample 2 is inserted into the cavity, its measurement spectrum is obtained together with the standard sample 17, and a correction process is performed using the stored measurement spectrum.

Now, ESR as shown in Figure 3a using only standard sample 17
It is assumed that a spectrum S1 has been obtained, and that the magnetic field sweep range at this time is Pq. Next, when the measurement sample is measured together with the standard sample, a spectrum S2 based on the standard sample appears in the magnetic field sweep range P-q, as shown in Figure 3b.
A spectrum X based on the measurement sample appears in the sweep range rs. Since the spectrum in FIG. 3b is the measurement result with the Q value of the cavity changed due to the insertion of the measurement sample, the correction value 1sx of the spectral intensity using the spectrum in FIG. It is determined from the following equation, assuming that the spectral intensities of S2 and X are 151, 152, and IX. This correction value 1sx is a value obtained by correcting the detection error caused by the measurement sample, that is, the attenuation of the signal intensity due to the decrease in the Q value of the cavity.

In the apparatus of the embodiment shown in FIG. 1, the intensity of the signal spectrum S1 with only the standard sample provided in the cavity is stored in the central control circuit 6.

Next, when the measurement sample is inserted into the cavity, the central control circuit 6
A signal for performing a magnetic field sweep in the same range as the signal spectrum S1 is generated, and the ratio of the signal intensity of the signal spectrum S2 of the standard sample obtained by the sweep to the signal intensity of the stored spectrum signal S1 is determined. is also the central control circuit 6
is calculated and stored. Then, the spectrum x obtained by measuring the sample under the same cavity condition is corrected using the signal intensity ratio as a correction coefficient, and the correct measured spectrum is displayed and stored. As described above, according to the present invention, as long as the same cavity is used, a correctly corrected measurement spectrum can be easily obtained no matter how many times the sample is exchanged. This makes it possible to accurately compare the intensity of spectra, and has a great effect on research on physical properties using an electron spin resonance device.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing an embodiment of the device of the present invention, and FIG.
FIG. 3 is a schematic diagram for explaining the principle of the present invention. 1: Cavity resonator (cavity), 2: Measurement sample, 6: Central control circuit, 7: Static magnetic field sweep circuit, 8: Microwave oscillator, 9: Magic T, 10: Mital wave detector, 11:
Coil for magnetic field modulation, 12: High frequency oscillator, 13: Phase detector, 14: Display device, 15: Waveguide, 18: Sample insertion glass tube.

Claims (1)

[Claims] 1. A cavity resonator in which an extremely small amount of a standard sample is always provided and a measurement sample is inserted is placed in a static magnetic field, and the absorption of microwaves generated within the cavity resonator by sweeping the intensity of the static magnetic field. In an apparatus for measuring a change in quantity as a spectrum signal in correspondence with a magnetic field sweep value, means for storing a measurement result of the spectrum signal S_1 in a state in which only a standard sample is provided in the cavity resonator; Spectrum signal S_2 based on the standard sample and measurement sample in the instrument
an electron spin resonance apparatus comprising means for measuring the intensity ratio of the spectral signals S_1 and S_2, and means for correcting the intensity of the measured spectrum of the measurement sample using the intensity ratio as a correction coefficient. .