Use of ruthenium dyes for subnanosecond detector fidelity testing in real time transient absorption (original) (raw)
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Transient absorption experimental set-up with femtosecond time resolution
The experimental set-up for time dependent transient absorption/gain measurements with femtosecond time resolution is presented. Using pump-probe spectroscopy technique with femtosecond pulses from Ti:Sapphire laser system (Spectra Physics), the optical density of transient absorption and transient gain in the spectral range of 330-700 nm, time resolution of 120 fs, can be measured with the precision of up to 0.005. Knowing the real time resolution and "zero time" dispersion of the system from two-photon absorption measurements, we performed femto-and picosecond study of electronically excited DCM molecule in c-C 6 H 12 and MeOH solution. The emission decay of the DCM molecule in the locally excited singlet state, S 1 -LE, was measured with picosecond time resolution using TCSPC set-up (Time Correlated Single Photon Counting). The steadystate and time resolved measurements permitted the determination of the properties of this locally excited singlet S 1 -LE state and the pathways of its deactivation. ᭧
Applied Spectroscopy, 2014
We present a new development for pump-probe absorption spectroscopy that allows the simultaneous measurement from the green part of the visible spectrum (510 nm) over the whole nearinfrared range to .1600 nm, corresponding to 0.77-2.40 eV. The system is based on a sub-picosecond supercontinuum generated in bulk material used as a broadband probe that is dispersed with a custom-made prism spectrometer and detected by an InGaAs array with extended sensitivity to the visible. Two versions, with and without probe referencing, are implemented for operation at laser repetition rates of a few hertz and kilohertz, respectively. After presentation of the optical configuration of the spectrometer, its performance is characterized and further illustrated on two time scales, with the ultrafast radiolysis of isopropanol induced by a picosecond electron pulse and with the instantaneous response of a BK7 plate to a femtosecond light pulse. The photophysics of the dye IR-140 is resolved from the femto-to picosecond regime. Stable and easy day-today routine use of the spectrometer also can be achieved in non-optical laboratory surroundings. For operation in a hazardous environment, the optical probe beams can be transported to the detector unit by optical fibers.
Polarization-controlled optimal scatter suppression in transient absorption spectroscopy
Scientific Reports, 2017
Ultrafast transient absorption spectroscopy is a powerful technique to study fast photo-induced processes, such as electron, proton and energy transfer, isomerization and molecular dynamics, in a diverse range of samples, including solid state materials and proteins. Many such experiments suffer from signal distortion by scattered excitation light, in particular close to the excitation (pump) frequency. Scattered light can be effectively suppressed by a polarizer oriented perpendicular to the excitation polarization and positioned behind the sample in the optical path of the probe beam. However, this introduces anisotropic polarization contributions into the recorded signal. We present an approach based on setting specific polarizations of the pump and probe pulses, combined with a polarizer behind the sample. Together, this controls the signal-to-scatter ratio (SSR), while maintaining isotropic signal. We present SSR for the full range of polarizations and analytically derive the optimal configuration at angles of 40.5° between probe and pump and of 66.9° between polarizer and pump polarizations. This improves SSR by 3 3 5 2 ≈. (or 3 compared to polarizer parallel to probe). The calculations are validated by transient absorption experiments on the common fluorescent dye Rhodamine B. This approach provides a simple method to considerably improve the SSR in transient absorption spectroscopy.
International Journal of Photoenergy, 2001
The aim of this paper is to provide the main pieces of information concerning the application of transient absorption (TA) spectroscopy with sub-picosecond laser pulses. A description of the experimental apparatus and of some detection schemes are included together with the most common mathematical formulas utilized to analyze the signals. The results, recently obtained in our laboratory and presented here, concern the investigation of the excited state dynamics of simple molecular systems. Examples of the measurements of the relaxation processes occurring in the lowest excited states of some aromatic molecules will be discussed in order to show the potentiality of the technique.
Dual wavelength optical sampling technique for ultrafast transient bleaching spectroscopy
Optics Communications, 1995
The ultrafast optical sampling technique has been successfully applied to the non-degenerate subpicosecond pump-probe spectroscopy by using two independently oscillating tunable femtosecond lasers with slightly different pulse repetition rates (fi, fJ. The choice of the pump and probe wavelengths is fully arbitrary within the tunability range of the two lasers with time resolution (-300 fs) limited only by the width of the cross correlation. In our method the difference frequencyf,-fi is locked to the frequency of an external reference for better temporal accuracy and introduction of the homodyne detection revealed a great improvement of sensitivity. The transient absorption bleaching measurements have been performed for organic dye molecules in solution to demonstrate the abilities of this technique. Signals of the time evolution of the photoexcited molecules ranging from subpicosecond intramolecular relaxation to nanosecond ground-state recovery, as well as picosecond solvation dynamics and subnanosecond orientational relaxation, are simultaneously detected in such a simple manner as varying the sweep time of the oscilloscope.
Laser-Raster Spectrometer for Time-Resolved Recording of Transient Absorption
Applied Optics, 1999
For measurements of transient absorption a laser-raster technique has been found to be surprisingly sensitive. It utilizes spatial separation of excitation and probing by employing a fast-flowing jet stream. The time resolution is determined by the flow velocity and the focal diameters of the continuous excitation and probing laser beams. Changes in transmission can be detected in the spectral region
Open hardware microsecond dispersive transient absorption spectrometer for linear optical response
Photochemical & Photobiological Sciences
An open hardware design and implementation for a transient absorption spectrometer are presented that has microsecond time resolution and measures full difference spectra in the visible spectral region from 380 to 750 nm. The instrument has been designed to allow transient absorption spectroscopy measurements of either low or high quantum yield processes by combining intense sub-microsecond excitation flashes using a xenon lamp together with stroboscopic non-actinic white light probing using LED sources driven under high pulsed current from a capacitor bank. The instrument is sensitive to resolve 0.15 mOD flash-induced differences within 1000 measurements at 20 Hz repetition rate using an inexpensive CCD sensor with 200 μm pixel dimension, 40 K electrons full well capacity and a dynamic range of 1800. The excitation flash has 230 ns pulse duration and the 2 mJ flash energy allows spectral filtering while retaining high power density with focussing to generate mOD signals in the 10–4...
Journal of Applied Physics, 2004
The submitted manuscript has been created by the University of Chicago as Operator of Argonne National Laboratory ("Argonne") under Contract No. W-31-109-ENG-38 with the U. S. Department of Energy. The U. S. Government retains for itself, and others acting on its behalf, a paid-up, nonexclusive, irrevocable worldwide license in said article to reproduce, prepare derivative works, distribute copies to the public, and perform publicly and display publicly, by or on behalf of the Government.