Ultraviolet-visible spectroscopy (UV-Vis) is a simple, rapid, and cost-effective core technology in the field of material characterization, playing an irreplaceable role in various areas such as organic molecular structure analysis and semiconductor material performance testing. However, most users can only initially identify peak positions and struggle to deeply explore the structural information behind the spectra. To address this, a systematic interpretation guide has been developed to help researchers and technical personnel easily master the entire process of skills from basic principles to practical applications.
    The core of this technology lies in capturing the transition energy of electrons from the ground state to the excited state, among which four key transition types form the foundation of spectrum interpretation. The σ→σ* transition has a wavelength of less than 150 nm with a high molar extinction coefficient, commonly found in saturated hydrocarbons; the n→σ* transition ranges from 150 to 250 nm with a medium extinction coefficient, mainly involving compounds containing lone-pair electrons such as O, N, and S; the π→π* transition is the most common type, with a wavelength range of 200-700 nm and an extremely high extinction coefficient, widely existing in conjugated systems; the n→π* transition has a wavelength of 250-600 nm with a low extinction coefficient, which is an exclusive feature of carbonyl compounds.
     Beer-Lambert Law (A=ε·c·l), as the core formula for quantitative analysis, has practical application value far beyond the formula itself. The absorbance (A) yields the most accurate measurement results in the range of 0.1-1.0, and the reasonable matching of molar extinction coefficient (ε), substance concentration (c), and optical path length (l) can achieve precise quantitative analysis. Mastering the mnemonic "π→π* is the strongest and most common, while n→π* is the weakest and hard to detect" enables quick preliminary judgment of material structural characteristics.
    Whether in the study of conjugated systems in organic chemistry or the band gap determination in the semiconductor industry, UV-Vis technology can provide key data support. This guide, covering from basic principles to advanced skills, will help users break through the limitations of traditional interpretation and give full play to the application potential of this technology.

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