INSTRUMENTATION:

The instrumentation for laser flash photolysis consists of a series of time-synchronized devices, and the measurement is triggered via a computer. A pulsed ns Nd:YAG laser (Quantel, Q-smart 450, 6 ns pulse duration, 10 Hz pulse repetition rate) is used to excite the sample, with excitation wavelengths of 1064 nm, 532 nm, 355 nm, and 266 nm, and maximum energy up to 450 mJ (power up to 195 MW/cm²). Detection is spectrophotometric and consists of a spectrometer with an Xe lamp capable of operating in pulse mode, a halogen lamp, a photomultiplier, and a monochromator (LP980, Edinburgh Instruments, spectral range from 200 to 800 nm, time range from several tens of ns to s), various optical components (mirrors and prisms), an oscilloscope, a computer, and software for data acquisition and processing.

TECHNIQUE:

The laser flash photolysis (LFP) technique monitors the kinetics of reactive short-lived species, such as excited triplet states of molecules, radicals, radical ions, and other reaction intermediates. In addition to kinetics, their transient absorption spectra are detected spectrophotometrically. The technique allows the determination of reaction mechanisms of very fast reactions occurring on time scales ranging from just a few tens of ns to µs and ms. The reaction systems may include solutions, suspensions, and various materials.

WORKING PRINCIPLE:

Light from an Xe lamp passes through the sample and then through a monochromator to the detector, while the laser pulse, arriving perpendicular to this light, excites the molecule. The change in sample absorbance at a specific wavelength over time is measured, which results from the difference in light absorption by the sample before and after the laser pulse. Additionally, it is possible to measure fluorescence lifetimes that can be temporally resolved given the 6 ns pulse duration of the laser used to excite the molecule.

APPLICATION - SERVICES:

• Mechanistic photochemistry, chemical kinetics, spectroscopy, radical chemistry
• Photophysical properties of molecules and photochemical reactivity
• Photodynamic therapy (lifetime of triplet excited states of molecules; their T-T absorption spectra; triplet quenching rate constants by oxygen)
• Study of crucial processes such as energy transfer, electron transfer, HAT (hydrogen atom transfer), PCET (proton-coupled electron transfer), SPLET (sequential proton-loss electron transfer) in various reaction systems
• ns laser ablation of various metals in solutions (synthesis of metal nanoparticles)
• Characterization of solar cells
• Photocatalysis
• Additional optical components needed for diffuse reflectance measurements suitable for opaque solid samples and highly reflective suspensions are planned to be purchased