JPH04143638A - Time resolving, absorbing and measuring apparatus - Google Patents

Abstract

PURPOSE:To simultaneously measure sample beam and reference beam by one apparatus by dividing probe beam into the sample beam irradiating a sample exciting beam irradiation part and the reference beam irradiating a nonirradiation part and independently introducing the spectrum data of both of them into one input slit. CONSTITUTION:Laser beam is separated into a fundamental wave omega and secondary and tertiary higher harmonics 2omega, 3omega by a prism 2 and the higher harmonic 3omega is timewise adjusted by a beam delay path 3 as exciting beam 20 to irradiate a sample 11 and the fundamental wave omega becomes white beam of a continuous spectrum by a cathode 10 to be timewise adjusted by a beam delay path 4 to become probe beam which is, in turn, split into sample beam S and reference beam R by a splitting means 22 to be timewise adjusted to simultaneously irradiate the sample 11. The beam S transmits through the irradiation part of the exciting beam 20 and the beam R transmits through a non-irradiation part to obtain respectively independent spectra in the upper and lower output slits of a spectroscope 13 and a slit image is formed on a streak camera 14 to be converted to a streak image polarized at high speed. The higher harmonic 2omega is timewise adjusted so as to synchronize to the exciting beam 20 and the probe beam 21 to trigger the sweep circuit of the camera 14. By this method, spectrum data and the timewise change data of intensity are simultaneously obtained.

Description

Detailed Description of the Invention "Industrial Application Field" The present invention has a time resolution of picoseconds (10-128),
From sub-nanoseconds (10-”s) to 30 nanoseconds (30× 1
The present invention relates to a time-resolved absorption measuring device for tracking photochemical reactions in a region of about 0-9s).

``Conventional technology'' When measuring the absorption of light by a material, the intensity of the incident light is measured to measure how much the light is attenuated as it passes through the sample. , the intensity of the transmitted light is expressed by the following equation.

I/Io=T (!accuracy), -uog T=A (absorbance)
Samples are also measured for solids and gases, but generally the fifth
Measure as a solution as shown in the figure. i.e. the same incident light weight. The intensity of transmitted light l5 for the solution and solvent respectively is
Find oln(λ, 1) and I5olv(λ, t),
Calculate the solute transmittance T from the following equation.

I 5oln(λ, t)/I 5olv(λ, t)=
TThis is due to the difference in light source intensity depending on the wavelength (λ), and also due to the difference in time (
1) This is to correct for fluctuations.

However, in Figure 6, a sample (11) is irradiated with excitation light (20) from a pulsed laser, and the spectra and intensity changes of the excited species and reaction intermediates generated in the sample (11) are measured using white probe light (21). The probe light (21) uses white light with a continuous spectrum, and after passing through the sample, it enters the streak camera (14) perpendicular to the sweep direction of the streak camera (14). An apparatus has been proposed in which the transient absorption spectrum and the change in intensity can be simultaneously observed by one shot of excitation laser oscillation by detecting the change in the intensity of the probe light using the streak camera (14).

In order to measure the newly generated absorbance change ΔA by optically exciting a sample using the above-described apparatus, first, the probe light weight is measured without irradiating the excitation light (20). (λ, 1) is measured. Hereinafter, this will be referred to as R light (reference light). Then, the measured value of this R light is temporarily stored in a two-dimensional memory. Then, the excitation light (20) is irradiated a second time to produce probe light r(λ.

t). Hereinafter, this will be referred to as S light (sample light). This is also stored in a two-dimensional memory, and a CPU or the like calculates S/R=T(λ, 1) from these data, and ΔA(λ, 1) is obtained as a result. Note that on the two-dimensional memory, λ is the X coordinate, and t is the X coordinate.

"Problems to be Solved by the Invention" As described above, two measurements are required to determine the transmittance T. At this time, since the emission intensity pattern of the probe light usually fluctuates, problems arise in the measurement results.

SUMMARY OF THE INVENTION An object of the present invention is to provide a system in which probe light is separated by a half mirror and simultaneously measured, and can be measured simultaneously with one device.

"Means for Solving the Problems" The present invention irradiates a probe light onto a sample that has been optically excited by irradiating pulsed light, and detects a change in the intensity of the probe light with a streak camera. In an apparatus for observing changes, the probe light splitting means splits the probe light, and one of the split probe lights is used as sample light to irradiate the part of the sample that is irradiated with the excitation light, and the other is used as sample light to irradiate the part of the sample that is irradiated with the excitation light. an irradiation means for simultaneously irradiating the portions of which the excitation light is not irradiated as a reference light, and at least one unit for inputting the sample light and the reference light into the input slit and outputting their respective spectral information. a spectrometer and a conductive means for introducing at least two pieces of spectral information of the spectrometer into one input slit of the streak camera, each independently, the sample light and the reference light by one streak camera; It is designed to measure both light and light at the same time.

"Operation" When a metal that easily emits electrons in a gas-filled sealed container is irradiated with light such as a laser, high-intensity white light is generated, and this white light is used as probe light. Further, harmonics of the laser source are used as excitation light for irradiating the sample. Furthermore, harmonics from the same laser source are used as a trigger for starting the deflection sweep of the streak camera (hereinafter referred to as a streak trigger). The probe light is split into two by the splitting means, and the irradiating means simultaneously irradiates the part of the sample irradiated with the excitation light as sample light and the part not irradiated as reference light. These sample light and reference light enter the input slit of the spectrometer. These two spectral information are introduced into the input slit of one streak camera by means of transmission means having the same optical path length so as not to overlap with each other, and the two spectra are simultaneously measured with this one streak camera.

"Example" Embodiments of the present invention will be described below with reference to the drawings.

(1) is a laser generator, specifically the fundamental wave (ω==
A Nd:YAG laser generator that generates IQ64nm) and a second harmonic (
2c, +=532 nm) generator (SHG) and a third harmonic (3ω=355 nm) generator (THG). (2) is a prism, and the above ω, 2ω
, 3ω are separated. (3) and (4) are respectively optical delay paths made of optical fibers, (5) and (5)... are optical connectors,
(6) is a PIN photodiode that converts a 2ω laser into an electric signal, and (7) and (8) are condensing lenses. (9
) is a white light generating device. For example, when no voltage is applied to a gas xenon lamp, when the cathode (10), which is made of a metal that easily emits electrons, is irradiated with an ω laser, it produces high brightness.

Moreover, it emits continuous white light from the UV region to the near-infrared region. This luminescence lifetime was about 30 ns (half width). (22) is a probe light splitting means, and this splitting means (22) includes a half mirror (23) that splits one probe light into two, a reflection mirror (24), and a time adjustment mirror (25). One probe light beam is focused on the sample (
11) Sample light (S light) irradiated to the excitation light irradiation part
The other probe light serves as a reference light (R light) that irradiates the part of the sample that is not irradiated with the excitation light. (11) is the sample to be measured, (12) is a delay circuit for synchronizing the streak trigger signal, and (13) is a spectrometer for extracting two transient absorption spectra separately. (13) causes the spectrum of light that has entered a specific portion of the slit on the entrance side to be emitted from a specific portion on the exit side.

An optical aberration type spectrometer is used as a spectrometer that performs this function, as shown in FIGS. 1 and 2.

Note that an example using two spectrometers will be described later based on FIG. 3. (14) is a streak camera for measuring the real time of optical phenomena in the picosecond range, and the spectrometer (14)
3) and a conducting means (2) with the same optical path length consisting of flexible fiber arrays (26) (27) as shown in Fig.
8). This transmission means (28) can also use an optical system such as a mirror or a prism. Also,
As shown in FIG. 2, the streak camera (14) has an input slit (32) that receives the two spectra.
), a relay lens (40), a photocathode (41) for photoelectrically converting the formed slit image, and an acceleration mesh electrode (42).
), a deflection electrode (43) that performs a high-speed deflection sweep in a direction perpendicular to the length direction (spectral incident direction) of the input slit (32), and a multiplication microchannel plate (44).
), a fluorescent screen (45) that converts into an optical image (streak image)
, an output relay lens (46). This streak camera (14) is coupled to a CCD camera (15) for conversion into one image signal. (16) is an analyzer that processes image signals, and (17) is a monitor TV for image projection.
, (18) is a computer for controlling external equipment, (19)
is a plotter for recording paper.

In the above configuration, the laser beam generated by the laser generator W (1) passes through the prism (2) as the fundamental wave ω(1064r+n
+) 2nd harmonic 2 (, + (532 nm), 3rd harmonic 3 ω (355 nm). Among these,
The third harmonic 3ω is adjusted for a predetermined time in an optical delay path (3), and is irradiated onto the sample (11) as excitation light (20). Further, the fundamental wave ω is focused on the cathode (10) of a xenon lamp (9) serving as a white light generator. Then, white light with a continuous spectrum is generated from this cathode (io), and this white light is focused by a lens (7) and passes through an optical delay path (
After adjusting the predetermined time in step 4), the probe light (21) is irradiated onto the sample (11). This probe light (21)
is divided into two by a dividing means (22), one as S light (sample light) and the other as R light (reference light), and both are irradiated onto the sample (11) at the same time by adjusting the time. At this time, the S light is irradiated to the irradiated part of the excitation light (20),
The R light is applied to other parts. These samples (11)
The S light and R light transmitted through the lens (8) are respectively directed to a specific point (2) of the input slit (29) of the spectrometer (13).
9a) (29b), and the spectrometer (13
), two spectra of S light and R light can be obtained independently from the upper and lower slits (30) and (31). The two spectral images of the upper and lower output slits (30) (31) are the same length flexible fiber array (26
) (27) and are introduced into the long sword slit (32) of the streak camera (14) side by side in the incident direction. When it enters the input slit (32) of the streak camera (14), the relay lens (40) activates the internal photocathode (41).
A slit image is formed. The photoelectrons converted at the photocathode (41) are:

It is accelerated by the accelerating mesh electrode (42) and deflected by the deflection electrode (4).
3) and is deflected at high speed in a direction perpendicular to the slit length direction (slit incidence direction), then multiplied by the microchannel plate (44) and optically transmitted by the fluorescent screen (45). It is converted into an image (streak image). At this time, the high-speed deflection needs to be synchronized with the passage time of photoelectrons, so the second harmonic 2ω is converted into an electrical signal by the PIN photodiode (6), and the delay circuit (1
After the time is adjusted to synchronize the excitation light (20) and probe light (21) in step 2), the internal sweep circuit of the streak camera (14) is triggered.

In the manner described above, spectral information of the light to be measured and information on temporal changes in intensity can be obtained simultaneously. This streak image is converted into an image signal by a CCD camera (15), processed by an analyzer (16), and sent to a monitor TV (17).
As shown in FIG. 4, the spectra of S light and R light are displayed independently. At the same time, the computer (18) performs calculations such as T (λ+1), ΔA (λ1t), etc., and signals are sent to the plotter (19) and printed on recording paper.

In the above embodiment, one optical aberration type spectrometer (13) was used, but since it is sufficient that the spectra of R light and S light are output independently, it is possible to It is also possible to use two spectrometers (13a) (13b) with the same characteristics. That is, the S light and R light that have passed through the sample (11) are transmitted through the optical fibers (33a) and (33b), respectively, to the entrance slits (13b) of the spectrometers (13a) and (13b).
29a) Introduced in (29b). These spectrometers (
13a) (13b) are mirrors (34a) (35a),
(36a) (37aL (34b) (3sb), (36
b) (37b), diffraction grating (38a) (38b).

The output of each spectrometer (13a) (13b) is the prism (3
9) to the same output slit, and connect the streak camera (
Spectral information of S light and R light is input into the slit (32) of 14) in the direction of the arrow shown in the figure. The following operations are similar to those described above.

In the above embodiment, the excitation light (20) and the probe light (2
In 1), the sample (11) was irradiated after time adjustment using the optical delay paths (3) and (4), but the sample (11)
The time may be adjusted after irradiation and before entering the spectrometer (13). In this case, the excitation light is delayed by a predetermined time using a mirror, a prism, etc., and the timings of the excitation light and probe light are matched.

In the above embodiment, the transmission spectrum of the sample (11) was measured, but the reflection spectrum may also be measured.

"Effects of the Invention" As described above, the present invention can measure the sample light and the reference light simultaneously, so the temporal fluctuations that occur in the conventional method can be canceled and accurate spectral information can be obtained. Furthermore, since the sample light and reference light can be measured simultaneously with one streak camera, the equipment is simple and there is no possibility of mismatched triggers. Therefore, it has picosecond time resolution and is suitable for measuring photochemical reactions in the subnanosecond to 30 nanosecond range.

[Brief explanation of drawings]

Fig. 1 is a block diagram showing an embodiment of the time-resolved absorption measuring device according to the present invention, Fig. 2 is a perspective view showing a coupled state of a spectrometer and a streak camera, and Fig. 3 is an explanation of another example of the spectrometer. 4 is a diagram showing an example of a video of a monitor TV, FIG. 5 is an explanatory diagram of solution measurement, and FIG. 6 is an explanatory diagram of a measuring device using a streak camera. (1)... Laser generator, (2)... Prism,
(3) (4)... Optical delay path, (5)... Optical connector, (6)... PIN diode, (7) (8)...
Lens, (9)... White light generator, (10)...
Cathode, (11) Sample, (12) Delay circuit, (13) (13a) (13b) - Spectrometer,
(], 4)-=streak camera, (15)...CC
D camera, (16)...analyzer, (17)...
Monitor TV, (18)...Computer, (19)...
- Plotter, (20)...Excitation light, (21)...Probe light, (22)...Dividing means, (23)...Half mirror 1 (24)...Reflection mirror, (25) ...
Time adjustment mirror, (26) (27)...Flexible fiber array, (28)...Transmission means, (2
9)...Input slit, (29a) (29b) -Specific point, (30) (31) ''Output slit, (32
)=-Manual slit, (33a) (33b)...Optical fiber, (34a) (34b) (35a) (3
5b) (36a) (36b) (37a) (37b
)-mirror, (38a) (38b)...'diffraction grating, (39)...prism, (40)...relay lens, (41)...photocathode, (42)...for acceleration Mesh electrode, (43)... Deflection electrode, (44)... Micro channel plate, (45)... Fluorescent screen, (46) Relay lens. Applicant Hamamatsu Photonics Co., Ltd.-21-l

Claims (1)

[Claims] (1) In an apparatus for observing a transient absorption spectrum or a change thereof by irradiating probe light onto a sample that has been photoexcited by irradiating pulsed light and detecting changes in the intensity of the probe light with a streak camera, the probe light one of the divided probe lights serves as a sample light that irradiates a portion of the sample irradiated with the excitation light, and the other irradiates a portion of the sample that is not irradiated with the excitation light; an irradiation means for simultaneously irradiating each as a reference light; at least one spectrometer for inputting the sample light and the reference light into an input slit and outputting their respective spectral information; and at least two of the spectrometers. and a conduction means for independently introducing two pieces of spectral information into one input slit of the streak camera, so that the sample light and the reference light can be simultaneously measured by one streak camera. A time-resolved absorption measurement device featuring: