JPH06222121A - Pulse fourier-transform electron spin-resonance device - Google Patents

Abstract

PURPOSE:To provide a pulse Fourier-transform ESR device which can provide high-resolution spectra by measuring FID signals at a sufficient level over a long period of time. CONSTITUTION:Microwaves generated from a microwave generator 3 are supplied as pulses via a microwave gate 5, a microwave amplifier 6 and a circulator 7 into a cavity resonator 2 disposed within a static magnetic field which a magnet 1 produces. The microwaves reflected from the cavity resonator because of the electron spin resonance of electrons are taken out via the circulator 7 and a gate 8 and are supplied to a quadrature phase wave detector 11. Two kinds of signal components obtained from the quadrature phase wave detector 11 are stored in a processor 14 via A-D converters 12, 13. A time function signal generated from a function generator 15 is supplied to an attenuator 9 as an attenuation factor control signal.

Description

Detailed Description of the Invention

[0001]

The present invention relates to electron spin resonance (ES).
R) device, in particular, pulse Fourier transform ESR device.

[0002]

2. Description of the Related Art In a pulse Fourier transform ESR apparatus, a spin system arranged in a static magnetic field is irradiated with a microwave pulse magnetic field for observation, and after irradiation, a response from the spin system excited by the microwave pulse magnetic field is measured. Signal (free induction decay signal, FID signal) is detected, and the obtained FID signal is converted into a digital signal and then Fourier-transformed to obtain ESR
I'm getting the spectrum.

FIG. 1A shows an example of an FID signal, in which the amplitude is exponentially attenuated according to a characteristic time unique to the spin system called relaxation time. Since the resonance frequency ν ₁ of the spin system does not necessarily match the frequency ν _{0 of the} irradiated microwave magnetic field, the difference frequency Δν = ν ₁ −ν ₀
A modulation component corresponding to the above appears in the above-described exponential decay function. Then, the ESR spectrum expanded in the frequency domain can be obtained by performing a Fourier transform on the observed exponential decay function.

[0004]

The relaxation time of electron spin treated by ESR is generally very short. In order to extract the modulation component contained in the attenuated signal, at least one period trigonometric function must be observed. However, in an actual device, as shown in FIG. 1B, since the signal attenuates earlier than this period, even if the Fourier transform is performed after the signal observation, the width is wide and the resolution is low and the information amount is small. There is a problem that only spectra can be obtained. Normally, a high-speed digital oscilloscope is used to acquire data in the time domain, but the signal strength quickly reaches a level at which the signal strength is considered to be zero due to the short-term attenuation of the signal, so the integration is performed. But no improvement was seen.

The present invention has been made in view of the above-mentioned points, and makes it possible to observe a signal that attenuates at a high speed at a sufficient level for a longer period of time than in the past, and thereby a high-resolution spectrum can be obtained. It is an object of the present invention to provide a pulse Fourier transform ESR device obtained.

[0006]

In order to achieve this object, the present invention irradiates a spin system arranged in a static magnetic field with a microwave pulse magnetic field for observation, and is excited by the microwave pulse magnetic field after irradiation. The response from the spin system is detected as a signal, and the obtained detection signal is converted to a digital signal and then Fourier-transformed.In a pulse Fourier transform electron spin resonance device, the gain is obtained in the signal system before the detection signal is converted to a digital signal. It is characterized in that variable means is arranged and means for controlling the gain variable means is provided in synchronization with the microwave pulsed magnetic field irradiation so that the gain of the gain variable means increases with time.

[0007]

According to the present invention, the gain varying means is arranged in the signal system before the detection signal is converted into the digital signal, and the gain varying means is synchronized with the microwave pulse magnetic field irradiation so that the gain increases with time. Since the means for controlling the gain varying means is provided, the gain increases so as to cancel the attenuation of the signal. Therefore, the signal can be observed at a sufficient level for a longer period of time than before. An embodiment of the present invention will be described below in detail with reference to the drawings.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 2 shows an embodiment of the present invention, in which 1 is a magnet for generating a static magnetic field. In this static magnetic field, the cavity resonator 2 in which the sample is inserted is arranged. The microwave generated from the microwave oscillator 3 is supplied to the cavity resonator 2 in a pulsed manner through the directional coupler 4, the microwave gate 5, the microwave amplifier 6, and the circulator 7. The reflected microwave from the cavity resonator, which is generated based on the absorption of microwave energy by the electron spin resonance of the sample, is taken out through the circulator 7 and the gate 8, and is detected by the quadrature detection through the attenuator 9 and the microwave amplifier 10. Is supplied to the container 11. The quadrature detector 11 performs quadrature detection using the microwave branched from the directional coupler as a reference signal, and the obtained two kinds of signal components are processed by the A / D converters 12 and 13 as processing devices. After being stored in 14, it is subjected to processing such as Fourier transform.

Reference numeral 15 is a function generator, and the generated time function signal is supplied to the attenuator 9 as an attenuation rate control signal. A memory 16 stores various time functions that can be generated by the function generator. By selecting one of the memories and setting it in the function generator 15, a desired time function signal can be generated. . Reference numeral 17 denotes a control unit that controls the timing of the entire apparatus, and controls a gate signal that controls ON / OFF of the gates 5 and 8, a control signal that controls the amplifier 6, and signal acquisition of the AD converters 12 and 13. Generates timing signals.

In the above structure, the microwave generated from the oscillator 3 is taken out as a microwave pulse by the gate 5 opened for a short time at the timing of FIG. 1 (c), and is amplified to a sufficient electric power via the amplifier 6. It is supplied to the cavity resonator 2 via the circulator 7. F from a spin system excited by this microwave pulse magnetic field
To detect the ID signal, the gate 8 is opened after the pulse as shown in FIG. 1 (d). When the attenuation rate of the attenuator 9 is constant, the FID signal obtained from the detector 11 is as shown in FIG.
As described in (b), it is attenuated in a short time as described above. Even if such a signal is introduced into the AD converter, the value of the signal immediately becomes 0 due to bit loss.

At this time, in the present invention, the attenuation factor of the attenuator 9 is changed with time according to the time function signal from the function generator 16. FIG. 1E shows the function generator 1.
6 shows a time function signal generated, and based on this signal, the attenuation rate of the attenuator 9 changes so that the attenuation rate is large at first and decreases with time as shown in FIG. 1 (f). . Therefore, the FID signal obtained from the detector 11 exhibits a gradual attenuation as shown in FIG. 1 (g), and the resonance frequency information is sufficiently transmitted through the AD converters 12 and 13. It is possible to capture the FID signal that includes it.

As described above, the change in the amplitude of the FID signal caused by the change in the attenuation rate with time is equivalent to that the filter processing, which has been digitally processed after the A / D conversion in the related art, is analogically executed. However, in the present invention, since filter processing is performed before sampling by the AD converter, it is possible to prevent bit loss during AD conversion for a small signal. In addition, a significant improvement in the SN ratio due to integration can be expected.

Also, the attenuation speed (relaxation speed) of the FID signal
Apparently grading corresponds to narrowing the line width of the frequency spectrum, which can improve the resolution of the spectrum. Further, the apparently gentle decay rate (relaxation rate) of the FID signal allows a change in the long period of the signal in the time domain to be more clearly extracted, so that a very small magnetic interaction appears on the spectrum. be able to.

The function for changing the attenuation rate may be an exponential function or another function such as a linear function or a quadratic function as long as the attenuation rate decreases with time. By using the memory 16 in which various time functions are stored and selecting one of them and setting it in the function generator 15,
The desired time function signal can be generated.

Although the attenuation rate is changed by the attenuator in the above embodiment, if the attenuation is considered to be a negative gain, it is sufficient to provide a gain varying means so that the gain increases with time.

[0016]

As described in detail above, according to the present invention,
Gain varying means is arranged in the signal system before the detection signal is converted into a digital signal, and the gain varying means is synchronized with the microwave pulse magnetic field irradiation so that the gain of the gain varying means increases with time. Since the control means is provided, it becomes possible to observe a signal that attenuates at a high speed at a sufficient level for a longer time than in the past, and thereby a pulse Fourier transform ESR device that can obtain a spectrum with high resolution is realized. .

[Brief description of drawings]

FIG. 1 is a waveform diagram for explaining the operation of an embodiment of the present invention.

FIG. 2 is a diagram showing an embodiment of the present invention.

[Explanation of symbols]

 1 Magnet 2 Cavity Resonator 3 Microwave Oscillator 4 Directional Coupler 5,8 Microwave Gate 6 Microwave Amplifier 7 Circulator 9 Attenuator 10 Microwave Amplifier 11 Quadrature Detector 12, 13 A-D Converter 14 Processor 15 Function generator 16 Memory 17 Control unit

Claims (1)

[Claims] 1. A spin system arranged in a static magnetic field is irradiated with a microwave pulse magnetic field for observation, and after irradiation, a response from the spin system excited by the microwave pulse magnetic field is detected as a signal and obtained. In a pulse Fourier transform electron spin resonance apparatus that performs a Fourier transform after converting a detection signal into a digital signal, a gain varying means is arranged in a signal system before converting the detection signal into a digital signal, and the gain of the gain varying means is time-dependent. A pulse Fourier transform electron spin resonance apparatus, characterized in that means for controlling the gain varying means is provided in synchronization with the microwave pulse magnetic field irradiation so as to increase with the passage of time.