JPH04136725A - Time resolved spectrometery - Google Patents

Abstract

PURPOSE:To enable a time-series spectrum in a reaction process to be measured simultaneously by acquiring a difference interferogram at a plurality of different delay times simultaneously and then performing their Fourier transformation. CONSTITUTION:Trigger signals from delay circuits 61, 62, 63... are combined by a trigger signal combiner 31, triggers are given to a power supply for light source 7 after delay times gamma1', gamma2', gamma3'... and t'+ gamma1', t'+ gamma2', t'+ gamma3'... after stimulating a sample 3 respectively, a pulse light source 1 is driven, and then a comb-shaped signal is obtained at a detector 4. This comb-shaped signal is sent to band-pass filters 111, 112, 113... according to a delay time by a distributer 32 and then an interferogram which is the difference between an excitation state and a normal state in each delay time can be taken out by lock-in amplifiers 121, 122, 123... which are connected to the next stage.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention periodically generates a stimulus using a stimulus generating means and repeatedly applies it to a measurement object, and uses a rapid scan interferometer using a pulsed light source to respond to the stimulus. The time-series spectrum of the reaction process of the measurement target can be obtained by obtaining the inter-7 erodalum of the difference from the normal state at different delay times after the stimulus of the measurement target that repeatedly shows the same response, and then obtaining the spectrum by Fourier transformation. Concerning a time-resolved spectrometry method for simultaneous measurements.

[Conventional technology]

The need to periodically apply stimulation to a sample using electricity, laser, or other means and measure the reaction state during the process of recovery from the stimulation is needed, for example, when evaluating the characteristics of liquid crystals, and in various other fields. be. As a measurement method, there is a time-resolved spectrometry method using FT-IR (Fourier transform infrared spectrophotometer). This method has been developed and used in the past because it can measure a wide wavenumber range with a high signal-to-noise ratio, and can be classified into those using a rapid scan interferometer and those using a step scan interferometer.

FT-IR uses an interferometer consisting of a semi-transparent mirror, a movable mirror, and a fixed mirror, and obtains an interferogram by moving the movable mirror. However, in an interferogram, characteristics such as transmittance of the sample remain constant during measurement. If the characteristics of the sample change, then when it is Fourier transformed, information different from the original information will be obtained. Therefore, in time-resolved spectroscopy, the period of stimulation applied must be longer than the time for the reaction to end, but when applying periodic stimulation, if the stimulation is applied regardless of the movement of the movable mirror, It is necessary to achieve that consistency. Therefore, conventionally, stimulation is applied in synchronization with a reference signal possessed by an interferometer.

Under these circumstances, the applicant has already developed a time-resolved spectrometry method that uses a rapid scan interferometer to obtain a time-series spectrum of the reaction state when a 1 J impulse is applied to the measurement target. l with a period longer than twice the reaction period
By repeatedly applying FI intensity and emitting light by controlling the delay time from stimulation with a period of 1/2 of the stimulation repetition period using a pulsed light source, and extracting the component that rides the stimulation repetition frequency from the detector output. By extracting, sampling, and Fourier transforming the interferogram that is the difference between the interferogram obtained from the sample in the excited state and the interferogram obtained from the sample in the normal state, the measurement target at each delay time and the normal state are obtained. We have proposed a time-resolved spectroscopic measurement method in which VFM is used to obtain the difference spectrum from the measurement target at
No. 28).

Since this method uses a pulsed light source as the light source, the time for irradiating the sample with light can be shortened, and the range of applications can be expanded.Furthermore, the stimulation can be applied asynchronously with the reference signal of the interferometer. , there are fewer restrictions on stimulation, and the stimulation frequency can be increased for faster responses, making it possible to improve measurement efficiency.Furthermore, it is possible to improve measurement efficiency by using a device equipped with a commonly used rapid scan interferometer. By adding systems such as gate circuits to the FT, data sampling circuits and data editing software, etc.
-rH can be implemented without requiring major changes to the system, and moreover, it can add the advantages of the differential measurement method.

This method will be briefly explained below. FIG. 5 is a diagram showing the configuration of an example of an apparatus for implementing the time-resolved spectrometry method according to the above proposal, and FIG. 6 is a waveform diagram for explaining its operation, in which 1 is a pulsed light source, 2 is the interferometer, 3 is the sample, 4
is a detector, 5 is a timer, 6 is a variable delay circuit, 7 is a power source for the light source, 8 is a frequency divider, 9 is a stimulus generator, 10 is a preamplifier, 11 is a bandpass filter, 12 is a lock-in amplifier, 13 is the main amplifier, 14 is the AD converter, 15 is C
Indicates PU.

In FIG. 5(a), sample 3 repeatedly shows the same response to the stimulus, and is the object of measurement of the reaction period τ as shown in FIG. 6(d). Timer 5 is 1, Figure 6, etc.)
As shown in FIG. 6(a), it generates a clock signal with a period t' (longer than the reaction period τ) which is asynchronous with the reference signal of the interferometer 2 shown in FIG. The frequency of the clock signal of 5 is divided by 1/2, and the divided period is 2t'.
This signal is supplied to the stimulus generator 9 and lock-in amplifier 12. The stimulus generator 9 gives a stimulus to the sample 3 as shown in FIG. 6(C) based on the signal generated by the 1/2 frequency divider 8. It is asynchronous with the reference signal. The variable delay circuit 6 is
It generates a trigger that is delayed by a fixed time Δτ' from the clock signal of the timer 5, and the light source power source 7 uses this trigger to drive the pulsed light source 1 at the timing shown in FIG. 2(e). be. Therefore, the signal from the sample in the excited state is
)cos2πa x d a and the signal from the sample in the normal state■ 1112t・(t-Δr'-t')fB(+7) co
s2rraxda becomes the output of the detector 9 alternately as shown in FIG. 6(f). The bandpass filter 11 is used to remove harmonics and low frequency components obtained from the output of the detector 9.

Therefore, the output signal of the detector 9 is filtered through a bandpass filter 11.
In order to see the output shown in FIG. 6(g) obtained when passing through 111at, (t-Δτ°) is Fourier transformed at t.

JIII2t, (t-Δτ) e'-”zrtdt=
e −+2””(1/2 t')uL72t・(
f ) −(1)=1/2t' [δ(f)+δ(f
1/2t') e-''2+δ(f-1/l')
e-””Igo・・・・・・・・・＋δ(f+1/2t
' ) e J2Lm□ + =... /2
t' δ (f-1/2t゛) e -''2χ-goshi5(-L'=t')=-1/2t'δ(f-1/2t
')e-""...(2). That is, both can be determined by Fourier transformation. As the bandpass filter 11, one that passes only these two terms is used. Therefore, the center frequency is 1/2 t', the bandwidth covers B(σ), 2B' (σ, Δτ'), and the output is f ( B' (σ, Δr') - B (+7) ) co
The interferogram of s2πa x d a is the frequency (
Therefore, the output signal is input to the lock-in amplifier 12, and the frequency (1/2t) is modulated.
2t') reference (hereinafter, blank space) By synchronizing with the signal, -f (B'(σ, Δτ') - B(σ)) cos2π
a x d a2t' is obtained. This results in taking out an interferogram that is the difference between the interferogram obtained from the sample in the excited state and the interferogram obtained from the sample in the normal state. Therefore, it is passed through the A/D converter 14 and the C
When taken into PU15 and subjected to Fourier transformation, B'(σ,
A difference spectrum of Δτ′)−B(σ) is obtained. Since processing is performed in the form of a difference spectrum in this way, the signal manually input to the A/D converter 14 can be compressed to compensate for the lack of dynamic range of the A/D converter 14. Deterioration of the SN ratio can be prevented.

In the above example, the timer 5 generates a clock signal with a period t', supplies this to the variable delay circuit 6, divides the frequency in the frequency divider 8, and supplies a signal with a period 2t' to the stimulus generator 9. However, as shown in FIG. 5(b), the timer 5' generates a clock signal with a period of 2t' and supplies this to the stimulus generator 9, which doubles the frequency of the clock signal of the timer 5'. It may be configured such that the signal is multiplied to twice the frequency by the circuit 8' and supplied to the variable delay circuit 6.

As described above, the invention according to the above proposal is an evolution of time-resolved spectroscopy into a difference measurement method.

The difference measurement method has the characteristic that it is not affected by changes in the state of the device or the measurement environment.

Note that the above invention is not limited to the above example, and various modifications are possible. For example, in the above example, the stimulus generator is controlled using the clock signal generated by the timer, and the pulsed light source is driven by delaying the pulsed light source by the time Δτ′ using the variable delay circuit. It is sufficient to configure the structure to emit pulsed light delayed by time Δτ' from the stimulus, so in the case of a light source that emits pulsed light with period t' by self-oscillation, such as a mode-locked pulse laser, the light source is monitored and then It may be configured to provide stimulation with a period delayed by t'-Δτ' and divided by 1x2.

In addition, in the above example, a t-pulsed light source was provided to stimulate the sample and emit light after a certain delay time, but instead of providing such a pulsed light source, a Raman excitation pulsed laser was used as shown in FIG. The sample may be excited using the following. That is, when the above invention is applied to a time-resolved FT-Raman apparatus as shown in FIG. 7, a Raman excitation pulsed laser 27 and a sample excitation pulsed laser 28 are used. Then, using the timer 24, frequency divider 25, and variable delay circuit 26, the sample excitation pulse laser 28 and the lock-in amplifier 31 are controlled by the 1/2 frequency divided signal of the clock signal of the timer 24, and the clock signal of the timer 24 is The Raman excitation pulse ray f27 is controlled at a timing delayed by Δτ' from t'. In this case as well, the sample excitation pulsed laser and lock-in amplifier are controlled by the timer clock signal as in the example shown in Fig. 5, etc., and the timer clock signal is multiplied by the frequency multiplier and variable delay circuit. The Raman excitation pulse laser may be controlled with a delay.

[Problem to be solved by the invention]

In the time-resolved spectrometry method proposed by the present applicant as described above, it is possible to measure the difference interferogram by applying pulsed light to the sample at a predetermined delay time after applying a stimulus. When attempting to measure the interferogram of the difference between several different delay times, it is necessary to repeat similar measurements by changing the delay time of the delay circuit 6.26, which takes a very long time.

The present invention was made in view of this situation, and
By using a rapid scan interferometer and a pulsed light source to simultaneously obtain interferograms of the differences at multiple different delay times for a stimulus, and then Fourier transforming them, it is possible to detect a measurement target that repeatedly shows the same response to a stimulus. It is an object of the present invention to provide a time-resolved spectrometry method in which interferograms of the difference from the normal state at different delay times are obtained, Fourier transform is performed, and time-series spectra in the reaction process are simultaneously measured.

[Means to solve the problem]

The time-resolved spectrometry method of the present invention that achieves the above object is a time-resolved spectrometry method that uses a rapid scan interferometer to obtain a time-series spectrum of the reaction state when a stimulus is applied to the measurement object. The stimulus is repeatedly given at a cycle longer than twice the response cycle, and a pulsed light source is used to emit light by controlling the delay time from the stimulus at half the cycle of the stimulus repetition cycle, and the stimulus repetition frequency is determined from the detector output. By extracting the interferogram of the difference between the interferogram obtained from the sample in the excited state and the interferogram obtained from the sample in the normal state, the interferogram is sampled and Fourier transformed. In a time-resolved spectrometry method that obtains a difference spectrum between a measurement target in time and a measurement target in a normal state, the pulsed light source is
emitting light at a plurality of different delay times per period of /2, separately extracting the detector output signal for each delay time, and extracting a component riding on the stimulus repetition frequency from each separately extracted signal. By obtaining a difference interferogram for each delay time, and performing Fourier transform on each difference interferogram to obtain a difference spectrum between the measurement target at the corresponding delay time and the measurement target in the normal state, the stimulus This method is characterized by simultaneously measuring the reaction state of a measurement target that repeatedly shows the same response to a plurality of delay times.

[Effect]

In the present invention, light is emitted from a pulsed light source at a plurality of different delay times per half of the stimulation repetition period, and a detector output signal for each delay time is separately extracted.
By extracting the component on the stimulus repetition frequency from each separately extracted signal, the interferogram of the difference for each delay time is obtained, and by Fourier transforming the interferogram of each difference, the interferogram of the difference at the corresponding delay time is obtained. By obtaining the difference spectrum between the measurement target and the measurement target in the normal state, it is possible to simultaneously measure the reaction state at multiple delay times of the measurement target that repeatedly shows the same response to IPJ stimulation. There is no need to repeat similar measurements by changing the delay time on the sample, and transient phenomena at different times when a stimulus is applied to the sample can be simultaneously measured in a short time.

〔Example〕

Next, embodiments of the time-resolved spectrometry method of the present invention will be described with reference to the drawings.

The basic idea of the present invention is that in the apparatus shown in FIGS.
Instead of emitting one pulse with a certain delay time per period of /2, multiple pulses with different delay times are emitted overlappingly.On the other hand, multiple channels consisting of bandpass filters, lock-in amplifiers, etc. By installing them in parallel and manually distributing the detector output signals corresponding to the pulses for each delay time to each channel, the results shown in Fig. 5 are obtained.
Based on the principle explained with reference to Figure 6, by simultaneously acquiring interferograms of differences at multiple different delay times after applying a stimulus and performing Fourier transform on them, the same response to the stimulus is repeatedly shown. This method simultaneously measures the spectral states at different times during the reaction process of the measurement target.

FIG. 1 is a diagram showing the basic configuration of an apparatus for implementing this time-resolved spectrometry method. Sample 3 shows the same response repeatedly to the stimulus, and FIG. As shown in Figure 6 (d), the reaction period τ is the object of measurement. The timer 5 is asynchronous with the reference signal of the interferometer 2 shown in Fig. 2(a) (same as Fig. 6(a)), as shown in Fig. 2(Q)) (same as Fig. 6(a)). A clock signal with a period t' longer than the reaction period τ is generated. This clock signal is divided in half by the frequency divider 8 to become a signal with a period of 2t', and based on this signal, the stimulus generator 9 applies the signal to the sample 3 as shown in FIG. 2(C). This stimulus is asynchronous with the reference signal of the interferometer 2. Up to this point, it is similar to FIG. 5. On the other hand, the clock signal of period t' generated by the timer 5 is input to a plurality of delay circuits 61, 62, 63, . . . arranged in parallel. The delay circuits 61, 62, 63... each have different delay times Δτ1', Δτ2', Δτ3'...
3'..., and t'+Δτ1', t'+Δτ2',
t'+Δτ3'... A trigger signal is sent later. The trigger signals from each delay circuit 61, 62, 63... are combined by the trigger signal combiner 31, and the second
Delay time Δτ after applying the stimulus shown in figure (b) to sample 3
1'△τ2', Δτ3'..., and t'+Δτ1'
t'+Δτ2', t'+Δτ3'... Later, a trigger is given to the light source power supply 7. This trigger causes the
The pulse light source 1 is driven at the timing of the waveform.

Since the pulse light source 1 is driven at the timing shown in FIG. 2(e) as described above, a comb-shaped signal is obtained on the detector 4 as shown in FIG. 2(f). In other words, for repeated stimuli, Δτ1′Δτ2′, Δτ3′
..., t' + Δτ1't' + Δτ2', t' + Δτ3'... This is the same as sampling only the detection signal when the gate is applied with a delay time of t' + Δτ3', and a comb-shaped interferogram. is obtained. This comb-shaped signal is input to the distributor 32 via the preamplifier 10. The distributor 32 includes a delay circuit 61.6 as a timing signal for distribution.
2. The outputs of 63... are connected, and the delay times from stimulation Δτ1', Δτ2', Δτ3'... and t
'+Δτ1', t'+Δτ2',t'+Δτ3'...
The comb-shaped signal from the detector 4 is distributed to the band-pass filters 111, 112, 113, etc. connected to the next stage according to the following. Therefore, each bandpass filter 111, 112, 113...
A horizontal signal as shown by the solid line is input to 11 to 3, and the 5th
As described in connection with Figure 6 and Figure 6, harmonics and low frequency components were removed, and an interferogram of each difference modulated at the frequency (1/2t'') was obtained, which was connected to the next stage. By synchronizing with the reference signal of frequency (1/2t') by each lock-in amplifier 121, 122, 123... The interferogram of the difference between the interferogram obtained from the sample in the normal state and the interferogram obtained from the sample in the normal state can be taken out at the same time.Then, the interferogram of each difference can be extracted from the main amplifier provided in the fifth [! 131.1
32, 133..., and the AD converter 141
．． 142, 143, etc., the reference signal of the interferometer is sampled at the period t to become a digital signal as shown in FIG. △τ2′, Δτ3′・
A difference spectrum representing the state of the sample 3 at ... is obtained at the same time. Therefore, the measurement time can be shortened compared to the previously proposed method. In the above example, the timer 5 generates a clock signal with a period t', this is supplied to the delay circuits 61, 62, 63, etc., and the frequency is divided by the frequency divider 8 to generate a signal with a period 2t'. was configured to supply the stimulus generator 9, but as shown in FIG. 5(b),
The timer 5' generates a clock signal with a period of 2t' and supplies it to the stimulus generator 9, and the clock signal of the timer 5' is doubled to twice the frequency by the frequency multiplier 8', which is then supplied to the delay circuit 61.6.
2.63... may be configured to be supplied.

Next, FIG. 3 shows an apparatus having another configuration for carrying out the time-resolved spectrometry method of the present invention. The difference from the case of FIG. 1 is that instead of using a plurality of delay circuits 61, 62, 63, etc. with different delay times corresponding to each channel, a repetitive pulse of period t' from the timer 5 is used. t'/n
A multiplication pulse generator 33 that multiplies the repeated pulses (n: an integer of 2 or more) is used, and this multiplied signal is applied to the light source power supply 7 as a trigger, and the multiplication pulse from the multiplication pulse generator 33 is The phase (delay time) from the stimulus is t'/n, 2 t'/n, 3 t'/n...
The present invention uses a pulse distributor 34 that distributes repetitive pulses with periods t' that differ by .times., and applies the pulses distributed by the pulse distributor 34 as a timing signal to the distributor 32. In the case of FIG. 1, the delay time of each channel can be set arbitrarily, but in this case, the delay time is limited to an integral multiple of t'/n, but the other operations are the same.

Next, when using a Raman excitation pulsed laser as shown in Fig. 7, interferograms at multiple different delay times are obtained simultaneously to measure the spectral state at different times during the reaction process of the sample. An example is shown in FIG. In this case, the light source power supply 7 shown in FIG.
Instead, a Raman excitation pulse laser 27 is used. Then, the clock signal of period t' generated by the timer 5 is sent to the delay circuits 61, 62, 63... and the trigger signal synthesizer 3.
1, the delay time from stimulation Δτ1′, Δτ2′Δτ3′
Convert the trigger to the Raman excitation pulse laser 2
It is sufficient to control the pulse oscillation of 7. In addition, in this case as well,
As shown in FIG. 3, instead of using the delay circuits 61, 62, 63, . . . and the trigger signal synthesizer 31, a multiplication pulse generator 33 and a pulse distributor 34 may be used.

In addition to the above, various modifications can be made to the apparatus for carrying out the spectroscopic measurement method of the present invention. For example, a self-excited light source such as SOR radiation may be used as the light source, and pulse signals may be distributed based on the signal. What is important in the apparatus for carrying out the spectroscopic measurement method of the present invention is that each channel is provided with a separate bandpass filter 11L1.
12.113... and lock-in amplifier 121.122
．． 123..., and various other modifications are possible. Accordingly, the above arrangement of devices is merely illustrative and is not intended to limit the invention.

〔Effect of the invention〕

According to the time-resolved spectrometry method of the present invention, light is emitted from a pulsed light source at a plurality of different delay times per half of the stimulation repetition period, and a detector output signal for each delay time is separately extracted. East j from each separately extracted signal
By extracting the component that rides on the high repetition frequency, an interferogram of the difference for each delay time is obtained, and by Fourier transforming the interferogram of each difference, it is possible to calculate the difference between the measurement target at the corresponding delay time and the normal state. By obtaining the difference spectrum from the measurement target, it is possible to simultaneously measure the reaction state at multiple delay times of the measurement target that repeatedly shows the same response to a stimulus. There is no need to repeat similar measurements, and transient phenomena at different times when a sample is stimulated can be simultaneously measured in a short time.

Furthermore, there are advantages to the difference measurement method, which is the premise of this method.

In addition, since the method of the present invention uses a pulsed light source as a light source, similar to the time-resolved spectroscopy method on which it is based, it is possible to shorten the time for irradiating the sample with light, broadening the range of applications, and stimulating can be applied asynchronously with the reference signal of the interferometer, reducing restrictions on stimulation.Also, for faster responses, the stimulation frequency can be increased, improving measurement efficiency. By adding a stimulus generator, a delay circuit, a passive pass filter, a lock-in amplifier, etc. to a commonly used device equipped with a rapid scan interferometer, FT-IR such as a data sampling circuit and data editing software can be realized. It has the advantage of being able to be implemented without requiring major changes to the system.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the basic configuration of an apparatus for carrying out the time-resolved spectrometry method of the present invention, FIG. 2 is a waveform diagram for explaining the operation of the apparatus shown in FIG. 1, and FIGS. FIG. 4 is a diagram showing the configuration of another apparatus for implementing the time-resolved spectrometry method of the present invention, and FIG. 5 is a diagram showing the configuration of an apparatus for implementing the time-resolved spectrometry method based on the premise of the present invention. , FIG. 6 is a waveform diagram for explaining the operation of the apparatus shown in FIG. 5, and FIG. 7 is a diagram showing the configuration of another apparatus for carrying out the time-resolved spectrometry method based on the premise of the present invention. 1... Pulse light source, 2... Interferometer, 3... Sample,
4...Detector, 5 and 5'...Timer, 6...Variable delay circuit, 7...Power source for light source, 8...Frequency divider, 8
'... Frequency multiplier, 9... Stimulus generator, 10... Preamplifier, 11.111.112.113... Band pass filter, 12.121.122.123... Lock-in amplifier, 13.131.132.133... Main amplifier, 14.141.142.143... AD
Converter, 15... CPU, 27... Raman excitation pulse laser, 28... Sample excitation pulse laser, 31...
- Trigger signal synthesizer, 32... Distributor, 33... Multiplying pulse generator, 34... Pulse distributor, 61.62.
63...Delay circuit evil π glimpse 4th volume night

Claims (1)

[Claims] (1) A time-resolved spectrometry method that uses a rapid scan interferometer to obtain a time-series spectrum of the reaction state when a stimulus is applied to a measurement target, in which the stimulus is repeatedly applied to the measurement target at a cycle longer than twice the response period. At the same time, the pulsed light source emits light by controlling the delay time from stimulation at a period of 1/2 of the stimulation repetition period, and the component at the stimulation repetition frequency is extracted from the detector output, thereby detecting the excited state. By extracting the interferogram that is the difference between the interferogram obtained from the sample and the interferogram obtained from the sample in the normal state, sampling it, and Fourier transforming it, the measurement target at each delay time and the measurement target in the normal state are determined for each delay time. In the time-resolved spectrometry method that obtains the difference spectrum between the pulsed light source and the pulsed light source, light is emitted from the pulsed light source at a plurality of different delay times per half of the stimulation repetition period, and the detector output signal for each delay time is separately obtained. The difference interferogram for each delay time is obtained by extracting the component on the stimulus repetition frequency from each separately extracted signal, and the corresponding delay is obtained by Fourier transforming each difference interferogram. Time characterized by simultaneously measuring the reaction state at multiple delay times of a measurement target that repeatedly shows the same response to a stimulus by obtaining a difference spectrum between the measurement target in time and the measurement target in a normal state. Resolved spectroscopy.