Picosecond Transient Absorption Spectroscopy SystempicoTAS

picoTASCan Easily Measure Short-Lived Intermediates.

Features Completely Covers Gap Time Region (1 ns ~ 20 ns)

In most of light induced phenomena, intermediates (transient species) play
important roles to determine reaction efficiency and final products, and single
reaction cycle often involves multiple intermediates which are observed in different
time and wavelength regions.

picoTAS can observe light absorption of these intermediates in wide range oftime and wavelength. Therefore, picoTAS can contribute to various researches ofrapid reactions and development of high-performance materials and devices.

 Measures Wide Time Range from 100 ps to s
 Broadband Wavelength Coverage from VIS to NIR Removes Fluorescence Signal
 Asynchronous Opera�on Compact Size / No Op�cal Bench Required (-ns model)
What is Transient Absorption Spectroscopy (TAS) ?
• Fast Time Resolved Absorption
Measurement• Detects and Identifies Short-LivedIntermediates• Both Non-Luminescent andLuminescent Intermediates aredetectable• Explores and Analyzes Multi-stepComplex Processes

Transient Absorption Spectroscopy (TAS) is a methodof first time-resolved absorption measurement. A
pulsed light (pump light) induces reactions of atarget sample, then subsequent processes areobserved by absorption change of probe light.
It is known that fluorescence lifetime measurement isalso a time resolved method, but information
obtained is limited to a fluorescent process at thefirst stage of the reaction (excited singlet state). On
the other hand, information about non-fluorescentprocesses in a wide time region (short-lived radicalspecies, charge transfer states, etc.) can be obtainedby TAS, so we can explore and analyze multi-stepcomplex processes.

What is the Difference between
picoTAS and Conventional Techniques?

Wide Applications


TargetAreaspicoTAS
fspsnsPump and Probe Method

μss

Nanosecond
Flash
Photolysis
methodNanosecond
Flash
Photolysis
methodGap Time Region

2ms

There are mainly two conventional transientabsorption (TA) techniques, Pump & Probe
method and Nanosecond Flash Photolysis
method. However these methods havedifficulty in measuring the time region from 1to 20 nanoseconds in which many importantphenomena exist.
picoTAS can measure wide time range including
this “Gap Time Region” (1 - 20 nanoseconds)
where conventional methods have hardlyobserved. In addition, picoTAS has a capabilityof eliminating the influence of fluorescence,
therefore, not only non-fluorescent but also
fluorescent intermediates can be detected andidentified correctly which have never been
observed so far.

TargetSamples

Fluorochrome-Labeled DNA
Photochromism
Optical Switching
TargetQuantum-Dot
Phenomena
Artificial Photosynthesis
Photocatalyst
Organic Solar Cell, etcFullerene
Porphyrin
 Photoreactive OrganicMolecule Various Metal Complex
 Titanium Dioxide
 Organic EL Device
 Carbon Nanotube, etc.











TargetFields

Excited Singlet State
Triplet StateElectron Transfer
Charge Separation
Radical Formation
Excimer Formation
Energy Transfer, etc.

Photochemistry
Photophysics
Photobiology
Nanoscience
Materials Chemistry
Energy Science
Environmental Science,etc.
3picoTAS System Configuration
Models – Coverage of Time and Wavelength
1600 nmpicoTAS Optical Unit・ 410 – 1600 nm

optical design minimizing chromatic aberration

800 nmNIR(Monochrometers, Optics, Sample Chamber, Detectors)
PC・ Double Beam Optical Systemhigh excitation efficiency for thin samples

・ Automatic shutter (pump, probe)
・ Probe Light Auto-Balancing Mechanism

400 nm

・ 2 mm Solution Cell Holder
・ Thin Film Holder
・ Oblique Incidence Excitation

VIScorrects light intensity fluctuation

Dedicated
Oscilloscopepsnsµs-ps (picosecond)modelsms-ns (subnanosecond)model

Photonic Crystal Fiber

Probe Light Source
High-Repetition-Rate Super Continuum Light Source
50-100 ps, 20 MHz, 410-1600 nm

Pump Light Source-ns model : Pulse Width 350 ps, 1 kHzOR-ps model : Pulse Width 25 ps, 1 kHz

Pump Light and Probe Light of picoTAS are Asynchronous

Principle: Randomly Interleaved Pulse Train (RIPT) Method

In the RIPT method, signal waveforms of both pump light and probe light are recorded by high-Pump 1st time

Pump 2nd time

Optics Letters, 41, 1498 (2016)

Pump kth timeHighlighted in Nat. Photon., 10 (2016), 285and Science, 352 (2016), 669.

speed detectors on each pump light irradiation. The delay time of a probe pulse just after the pumppulse is calculated from these waveforms. Each light intensity of probe light pulse that is transmitted

Pump

through a sample is recorded by using a detector with amplifier, and the intensity is plotted basedProbeon the delay time. When pump light irradiation is repeated, the delay time differs every time
because pump light and probe light are asynchronous. In this way, the plot generates a continuous
curve after many-time pump light irradiation. By executing delta optical density calculation, transientabsorption curve is reconstructed.
4Reconstructed windowt d [1]

DetectedSignal

t d [2]t d [k]I
Delta Op�cal Density
Calcula�ontd5

Completely Covers Gap Time Region (1 ns ~ 20 ns)

Broadband Wavelength Coverage from VIS to NIR

The conventional methods have difficulty in measuring from 1 to 20

Recently, near-infrared measurements in transient absorption spectroscopy
are highly demanded. As picoTAS uses a super-continuum light source

nanoseconds, but picoTAS allows us to measure this “Gap Time Region”
which has almost never been studied so far.

In the Gap Time region, there exists various states andprocesses inside and among molecules.
“Excited Singlet State”
the initial excited state of many photochemical reaction“Excited Triplet State”
the second excited state which plays a key role indetermining the reaction products“Radical Species”
highly reactive intermediate stateObtain Transient Absorption
Temporal Profile
at Every Wavelength

Gap Time Region
Pump & Probe

nsFP

Excited Singlet

Super-continuum light source used as theprobe light source in picoTAS emits light in a
broad wavelength range from visible to nearinfrared region. Though its light intensity haswavelength dependence, picoTAS can adjust
the light intensity automatically which enters
into detectors.

Observable
PhenomenaIntersystem
Crossing (ISC)

Excited Triplet

Nanosecond Flash Photolysis(nsFP)

Radical Formation, Electron Transfer, etc.

Gap Time Region

fsps

ns

Wave length
Spectrum power density

picoTAS

picoTAS

Spectrum power density

Benzophenone in Acetonitrile
Probe at 550 nm

for the probe light source, a broad wavelengths range from visible (> 410nm) to near-infrared region (< 1600 nm) can be covered seamlessly.

msµss

Select Time to Extract
Transient Absorption Spectra

Pump & Probe

Measures Wide Time Range from 100 ps to ms

Display and Save the Spectra

picoTAS can measure a wide time range. It covers more than 6 orders ofmagnitude from 100 picosecond to millisecond, from formation to full decayof intermediates.
C60 in Toluene

Ir(ppy)3 in THF

Future Prospect
By combina�on with picosecond probe light sources of infrared or X-ray region,
studies of wider wavelength region (energy region) can be realized.
67

Data Example

In conventional nanosecond flash photolysis measurements, luminescence fromthe sample often interferes with the signal. Since picoTAS has an ingenious

Comparison of Time Resolution（10-90% Rise Time）

way to remove luminescence signal, we can obtain accurate transient absorption(TA) signal of excited singlet and triplet, etc.
Conventional nanosecond
Flash Photolysis

time resolution (<100 ps for -ps model, <400 ps for -ns model) is comparable to TCSPC fluorescence lifetime
measurements, so picoTAS can be widely applied to many reactions including non-luminescent samples.

picoTAS-ps model<100 pspicoTAS-ns model<400 ps

Typical Data fornanosecond Flash Photolysis～ 10 ns

Observation of the fast (<10 ps ) ISC of palladium porphyrin

TA signals covered by fluorescence

Accurate TA signals without ﬂuorescence

TA spectrum covered by fluorescence

RIPT method used inpicoTAS, by picking up the signal

intensity just before the rise ofeach probe pulse signal andrepeating this procedure for aseries of pulse train data set, abaseline
curveincludingluminescence such as fluorescenceand phosphorescence can bereconstructed. By subtracting thebaseline curve from individual
probe pulse train data, and thenpicking up probe light intensity,
pure TA signals, where emission
signals are removed, can beobtained.

at 900 nm

Samples Courtesy of Prof. R. Katoh, Nihon Univ.

Accurate TA spectra without ﬂuorescence

Luminescence Signal Removal in picoTAS
theFigure Courtesy of Dr. T. Suenobu, Osaka Univ.

High Sensitive Transient Absorption
Measurement of Photocatalyst
To elucidate the photoreaction mechanism of titanium dioxide
which shows remarkable behavior as a photocatalytic material, it
is known that the pump light intensity must be reduced anddetection of very small TA signals is required. In thismeasurement, picoTAS catches less than 1 mOD changes(equivalent to 0.025% transmittance change) in nanoseconds
time region.

ﬂuorescenceIn

picoTAS has 100 times higher time resolution than conventional nanosecond flash photolysis systems. The

picoTAS

ﬂuorescence8

picoTAS

Removes Fluorescence Signal

Fullerene (τ ISC ≃ 1 ns)
Fullerene is an promising material for electron acceptors of organic thinfilm solar cell and its time constant of intersystem crossing (ISC) isknown ~1 ns, so it is difficult to measure TA of this attractive reagent byboth pump & probe and nanosecond flash photolysis methods. With theuse of picoTAS, the spectra of the excited singlet, ISC and triplet state
can be clearly observed from visible to infrared wavelength region. Also,a complete decay curve of the triplet with lifetime of microseconds canbe observed.

ISC

Pump 355 nm, 25 ps
500 nm～1250 nm

Minimum Bin 50 ps

Tn←T1

Sn←S1

S1 decay9Specifications
ModelpicoTAS-nsMethodTime Resolution (10%-90% Rise Time)
Delay Time ResolutionTime Window
Wavelength Range
Automatic Control
Sample Holder
Light Source
Pump Light

Probe Light

PC &Software

picoTAS-ps

RIPT method (Randomly Interleaved Pulse Train method)<400 ps<100 ps

10 ps, 20 ps, 50 ps, 100 ps, 200 ps, 500 ps, 1 ns, 2ns, 5 ns, 10 ns, 20 ns

100 ns ～ 2 ms
410 ～ 1600 nm
Wavelength Scan, Light Intensity Adjustment, Shutter ControlSolution （Optical Path Length of 2mm）、Thin Filmpicosecond Mode-Locked Laserpassive Q-SW Microchip Laser
532 nm and/or 355 nm
532 nm and/or 355 nm
and/or 266 nm<350 ps<25 ps>10 μJ>80 μJ
100 - 1000Hz （variable）
1000 Hz
Picosecond Supercontinuum Light Source<50-100 ps （dependent on wavelength）
20 MHz ± 5%
Windows 7/10

Wavelength
Pulse Width
Pulse Energy
Repetition Rate
Light Source
Pulse Width
Repetition RateOS

Automatic Reconstruction of Transient Absorption Temporal Profile,
Conversiont to Transient Absorption Spectra, Curve Fitting (Nonlinear Least
Square method), Data Storage in Text Format

Function

Installation Environment

No Optical Bench Required

On Optical BenchpicoTAS Models (Coverage of Time and Wavelength)“Gap Time Region”
Diﬃcult to Measurewith Conven�onalMethods

1600 nmPump & Probe Method

Nanosecond Flash
Photolysis Method

680
Top View
pump light source
installation spacefor -ns model

480

Installation spaces for probe light source, PC andoscilloscope are needed separately.
-ps model further requires an installation space forpump light source.

Back View

Front View
225

Options

Wavelength-Tunable Pump
Light Source for -ps model
Excitation Wavelength Can be
Varied.
Type

Optical Parametric Generator (OPG)

Pump Laser

Picosecond mode-locked laser 1kHz, 355nm, 0.3W

Wavelength Range410-709 nm, 710-2300 nm

Pulse Energy

50µJ@450nmCoolSpeK Low-Temperature Cell
Holder (for 2mm cell)pump light source
installation spacefor -ns model

Customization
We will construct a customized system withexisting pump source, probe source in your lab.
Recommended
Specification
for Pump Light
SourceRecommended
Specification
for Probe LightSource

800 nmNIR
VIS

Temperature Range-80℃ ～ Room Temperature（~100°C）

Temperature Control

Flow control of liquid nitrogen by anautomatic valve

Functions

Low Dew Condensation by Heating of
Optical Window, Stirrer

Liquid Nitrogen
Reservoir

Stainless, 2L
Duration of 2H at -80℃

Global Analysis Software
400 nmSpectrum Analysis of Multicomponent
and Various Analysis Functions

psns-ps（picosecond ）modelµs

mss-ns（subnanosecond )model

SoftwareAnalysisFeatureOS

Repetition rate
Pulse width
Output energy

1 kHz,<500 ps,
20 μJ/pulse※Please contact us for the source out of
the specification above① Supercontinuum light source withrepetition-rate of 20 MHz② Supercontinuum light source equippedwith a pulse picker (Settable at 20MHz. ）③ Picosecond laser diode with highoutput energy (100nJ/pulse)

Temperature Range from -80°C to+100°C

fs

10

Dimensions of Optical Unit

Notes: System performance might be limited depending on thespecifications of pump light source and/or probe light source.

■ Single Wavelength Measurement by
Picosecond Diode Laser
Probe LightSource

Picosecond Diode Laser

Wevelength (nm)450, 532, 1000, 1100, 1200, 1300, etc.

Pulse Width

Dependent on Light Source Selected
200 ps@532 nm, 50 ps@1000 nm, etc

Globalworks - made by US Company OLIS
Singular Value Decomposition (SVD),
Global Fitting
Lifetime Calculation, Selection of Reaction
Mechanism Model
Windows XP/7

■ Please feel free to contact us for the transientabsorption system that can eliminate long-lived
luminescence by making the most use of the RIPT
method and a lower repetition-rate supercontinuum
light source.
11Unisoku has been developing this product in cooperation with Nihon University, Osaka University and Meijo University in theframework of the Japan Science and Technology Agencyʼs “Development of Systems and Technologies for Advanced Measurement
and Analysis (JST-SENTAN)” program.
The contents of this catalog are subject to change without prior notice for improvement.
Reproduction or copying the contents of this catalog in part or whole is prohibited without permission of Unisoku.
Catalog No.
UBPT 2023-06A

UNISOKU Co., Ltd.
E-mail: info@unisoku.co.jp

Web site: https://www.unisoku.com/

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