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| title | chunk | source | category | tags | date_saved | instance |
|---|---|---|---|---|---|---|
| Ultraviolet–visible spectroscopy | 5/5 | https://en.wikipedia.org/wiki/Ultraviolet–visible_spectroscopy | reference | science, encyclopedia | 2026-05-05T10:06:41.378064+00:00 | kb-cron |
== Microspectrophotometry == UV–visible spectroscopy of microscopic samples is done by integrating an optical microscope with UV–visible optics, white light sources, a monochromator, and a sensitive detector such as a charge-coupled device (CCD) or photomultiplier tube (PMT). As only a single optical path is available, these are single beam instruments. Modern instruments are capable of measuring UV–visible spectra in both reflectance and transmission of micron-scale sampling areas. The advantages of using such instruments is that they are able to measure microscopic samples but are also able to measure the spectra of larger samples with high spatial resolution. As such, they are used in the forensic laboratory to analyze the dyes and pigments in individual textile fibers, microscopic paint chips and the color of glass fragments. They are also used in materials science and biological research and for determining the energy content of coal and petroleum source rock by measuring the vitrinite reflectance. Microspectrophotometers are used in the semiconductor and micro-optics industries for monitoring the thickness of thin films after they have been deposited. In the semiconductor industry, they are used because the critical dimensions of circuitry is microscopic. A typical test of a semiconductor wafer would entail the acquisition of spectra from many points on a patterned or unpatterned wafer. The thickness of the deposited films may be calculated from the interference pattern of the spectra. In addition, ultraviolet–visible spectrophotometry can be used to determine the thickness, along with the refractive index and extinction coefficient of thin films. A map of the film thickness across the entire wafer can then be generated and used for quality control purposes.
== Additional applications == UV–Vis can be applied to characterize the rate of a chemical reaction. Illustrative is the conversion of the yellow-orange and blue isomers of mercury dithizonate. This method of analysis relies on the fact that concentration is linearly proportional to concentration. In the same approach allows determination of equilibria between chromophores. From the spectrum of burning gases, it is possible to determine a chemical composition of a fuel, temperature of gases, and air-fuel ratio.
== See also == Applied spectroscopy Benesi–Hildebrand method Color – Vis spectroscopy with the human eye Charge modulation spectroscopy DU spectrophotometer – first UV–Vis instrument Fourier-transform spectroscopy Infrared spectroscopy and Raman spectroscopy are other common spectroscopic techniques, usually used to obtain information about the structure of compounds or to identify compounds. Both are forms of vibrational spectroscopy. Isosbestic point – a wavelength where absorption does not change as the reaction proceeds. Important in kinetics measurements as a control. Near-infrared spectroscopy Rotational spectroscopy Slope spectroscopy Ultraviolet–visible spectroscopy of stereoisomers Vibrational spectroscopy
== References ==