Broadband ultraviolet-visible transient absorption spectroscopy in the nanosecond to microsecond time domain with sub-nanosecond time resolution

Abstract

A combination of sub-nanosecond photoexcitation and femtosecond supercontinuum probing is used to extend femtosecond transient absorption spectroscopy into the nanosecond to microsecond time domain. Employing a passively Q-switched frequency tripled Nd:YAG laser and determining the jitter of the time delay between excitation and probe pulses with a high resolution time delay counter on a single-shot basis leads to a time resolution of 350 ps in picosecond excitation mode. The time overlap of almost an order of magnitude between fs and sub-ns excitation mode permits to extend ultrafast transient absorption (TA) experiments seamlessly into time ranges traditionally covered by laser flash photolysis. The broadband detection scheme eases the identification of intermediate reaction products which may remain undetected in single-wavelength detection flash photolysis arrangements. Single-shot referencing of the supercontinuum probe with two identical spectrometer/CCD arrangements yields an excellent signal-to-noise ratio for the so far investigated chromophores in short to moderate accumulation times.

Physicochemical and Electronic Properties of Cationic [6]Helicenes: from Chemical and Electrochemical Stabilities to Far‐Red (Polarized) Luminescence

“…[ 19 ] The early transient spectra exhibit both negative and positive bands. The negative bands coincide with the stationary electronic spectra and can thus be attributed to both the bleach of the ground-state absorption and the stimulated S 1 →S 0 emission.…”

Temporal and spectral correlations in bulk continua and improved use in transient spectroscopy

“…In related work and discussions of the detection limit of broadband spectrometers that also use two-camera/chopper referencing not a single-filament continuum but a multifilament is used [32]. This results in as much as 10% fluctuation of the continuum at single wavelengths [7] that has to be averaged out subsequently.…”

“…However, an even better sensitivity and in particular a higher fidelity, i.e., the certainty that apparent spectral structures are indeed molecular signatures, is highly desirable. A method to enhance the sensitivity of the system is single-shot referencing [7,[28][29][30][31][32]. For this purpose a second identical CCD (reference camera) is installed and read out with the same technique as the first camera (sample camera).…”

“…Equation (5) is identical to the procedure described by others [7,26,30,32]. Since subsequent pulses are compared, the differing attenuation factors A S and A R cancel and an explicit calibration is not needed.…”

Comparison of Charge-Transfer Dynamics of Naphthalenediimide Triads in Solution and π-Stack Architectures on Solid Surfaces

“…[35][36]. Excitation was performed either at 532 or 355 nm using a passively Q-switched, frequency doubled or tripled Nd:YAG lasers (Teem Photonics, Powerchip PNG-M02010, Powerchip NanoUV) producing pulses at 500 Hz repetition rate, with approx.…”