Characteristics of UV-VIS Spectrum:
In sequence to acquired a UV-VIS spectrum the sample is ideally irradiated along with the electromagnetic radiation varied over a range of wavelength. A monochromatic radiation that is, a radiation of a single wavelength is employed at a time. This procedure is called scanning. An amount of the radiation absorbed at every wavelength is measured and plotted against the wavelength to acquire the spectrum. Therefore, a typical UV spectrum is a plot of wavelength or frequency versus the intensity of absorption.
Have a look again at Figure (b). The abscissa (x-axis) implies the wavelengths absorbed and therefore, is marked in wavelength by sometimes frequency might also be used. An ordinate (y-axis) on the other hand represents the intensity of absorption and is commonly represented in terms of absorbance. The UV spectra of substances are characterized through two main parameters, namely, the position of the maximum of the absorption band called λmax, and the intensity of the bands. Here λmax refers to the wavelength of the most absorbed radiation and is a measure of the difference in the electronic energy levels included in the transition. The intensity instead is indicative of the probability of the transition i.e., whether the transition is permitted or not. It is also is a measure of the concentration of the absorbing species. A relationship among the intensity of absorption.
The features of UV-VIS spectrum depend on the structure and concentration of the absorbing species in solution. Thus, these spectra are extensively used within the characterization and in the quantitative estimations of the analyte.