Ultrafast transient absorption spectroscopy uses a pulsed laser to excite the electrons that are attached to the given molecule that is being observed or studied. The goal of the this method is to bring the electrons to a heightened state of excitement with the use of a probing light source, that usually comes from a xenon arc lamp and is used to gain visibility of an absorption spectrum of the compound that is being studied, so that we can look at it during various times of the excitation of the electrons.
This process gives us the ability to observe the transitory states that molecules and electrons go through when they are provoked by an intense amount of photophysical and photochemical reactions.
Principles of Ultrafast Transient Absorption Spectroscopy
When energy transfers happen in a photosynthetic membrane, it happens so quickly that it would be impossible to observe the changes with the human eye, even with the most refined microscope. These reactions happen on time scales that can be measured in less than 100 femtoseconds to hundreds of picoseconds.
Thankfully, the innovations that experts made to turnable lasers in the 1990’s has made this fascinating and informative area of study possible, and has opened us up to brand new research and information about the transitional stages of photochemical and photophysical reactions that occur to molecules and other materials.
Happenings During Testing
What happens during testing is that experts use a set of two different pulses to study the molecule or material in question. They use the first pulse which is known as the pump pulse to excite the material and the electrons of that molecule or material. Then they transmit a second, smaller, less-intense probe pulse which is on a set delay from the pump pulse. And experts then measure the difference in the absorption spectrum of the materials by first subtracting the absorption state of the excited materials from the absorption state of the grounded materials.
By changing the time delay between the initial pump pulse and the probe pulse, we are able to observe the electron and proton changes of materials at different points in time during the process which gives us a spectrum of the dynamic processes and changes that these materials go through during this photosynthetic process.
In studying materials using ultrafast transient absorption spectroscopy, we can discover so much more about the spectrum of physical and chemical dynamics that occur in molecules and materials when they are exposed to lasers and intense light exposure.
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