Emission Spectroscopy
In the case of Emission Spectroscopy, the spectra are obtained from the radiation of the sample itself with no need of an external irradiating source. If the detector of the spectrometer is used at room temperature, the sample must be heated or cooled to attain the spectra for which purpose Microptik has developed heating and cooling stages and sample chambers. In case the detector operates at low temperature, heating or cooling is not necessary and the analysis can take place at room temperature. As a general rule, emission spectra increase at higher temperature.
ES is a nondestructive sampling technique and is particularly useful for films on rough metal surfaces and catalysis studies where other techniques fail. Some of these applications is the characterization of impurities in microscopic craters and crevices pollutants spectra analysis and catalysts poisoning or deactivation studies.
The nature of the sample, as for example particle size and concentration which affect surface to volume ratio and reabsorption of emitted radiation, respectively, is a very influent factor.
Emission spectra are almost similar to transmission spectra, but inverted since regions of high transmissions are regions of low emmision. The bands are narrower and may sometimes present inverse peaks when compared to the other sampling techniques, due to selective reflection and reabsorption phenomena. This arouses from the expression for emissivity, E=1-T-R, when the reflectivity at certain frequencies is not low enough to be neglected.
Although emission can be collected by using mirrors to enhance the signal, modern configurations using fiber optics or large solid angles with ellipsoidal or paraboidal mirrors can be used for improving the collection of spectra. Microptik provides these kind of accessories to increase the signal to noise ratio.


