Question

Uv visible spectroscopy principle and instrumentation

Answer 1

Principle- Molecules containing π-electrons or non-bonding electrons (n-electrons) can absorb the energy in the form of ultraviolet or visible light to excite these electrons to higher anti-bonding molecular orbitals. The more easily excited the electrons (i.e. lower energy gap between the HOMO and the LUMO), the longer the wavelength of light it can absorb. There are four possible types of transitions (π-π*, n-π*, σ-σ*, and n-σ*), and they can be ordered as follows: σ-σ* > n-σ* > π-π* > n-π*.