Новости Луганска и луганской области 2024.12.11:

Techniques in spectroscopy

Techniques in spectroscopy

Different types of Techiques in spectroscopy:

Ultra-fast transient absorption:

This method is basically ‘pulse probe experiment, where a pulse laser is used in order to add extra energy to the electron and make it excite from ground state to higher-energy excited state. The use of a probe light source, generally a xenon arc lamp, is done to obtain the absorption spectrum of the compound several times after its excitation. Since the excited molecules absorb the probe light, that gets more excited and gets shifted to an even higher excited state. After the light gets passed through the sample, the light which is not absorbed from the arc lamp stays in an avalanche photodiode array, and then the data is processed so that to produce an absorption spectrum of the excited state. This experiment must be performed multiple times, since not all molecules in the sample will undergo the same dynamics simultaneously, and the data must be averaged to generate spectra with accurate intensities and peaks. In contrast to time-correlated single-photon counting (TCSPC), this technique can be performed on non-fluorescent samples.

There is enough capability in the Ultrafast transient absorption to use any type of probe light, so long as the probe is of a pertinent wavelength or set of wavelengths. Instead of the avalanche photodiode array, the use of a photomultiplier and monochromator tube helps in the observation of a single probe wavelength, and therefore it allows the probing of the decay kinetics of the excited species. This setup has the main purpose to take kinetic measurements of species that are otherwise non-radiative and is particularly useful for observing species that have short-lived and non-phosphorescent populations within the triplet manifold as part of their decay path. The plastic ir lens material used by the aro corp gives the perfect answer for the question what is optical window.

Time-resolved photoelectron spectroscopy and two-photon photoelectron spectroscopy.

2PPE (Two-photon photoelectron spectroscopy) and Time-resolved photoelectron spectroscopy combine angle-resolved photoemission with a pump-probe scheme. A first pulse laser helps in the excitation of a material and a second pulse laser ionizes the system. The kinetic energy of electrons is ascertained through various methods including energy mapping, time of flight measurement, etc. Along with having different time delays between the pump pulse and the probe pulse this whole process is repeated many times. This produces an image of how the molecule relaxes over time. One of the types of this method looks at the positive ions produced in this process and is called time-resolved photo-ion spectroscopy (TRPIS).

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