In spectroscopy, hypsochromic shift () is a change of spectral band position in the absorption, reflectance, transmittance, or emission spectrum of a molecule to a shorter wavelength (higher frequency). Because the blue color in the visible spectrum has a shorter wavelength than most other colors, this effect is also commonly called a blue shift.[1] It should not be confused with a bathochromic shift, which is the opposite process – the molecule's spectra are changed to a longer wavelength (lower frequency).
Hypsochromic shifts can occur because of a change in environmental conditions. For example, a change in solvent polarity will result in solvatochromism. A series of structurally related molecules in a substitution series can also show a hypsochromic shift. Hypsochromic shift is a phenomenon seen in molecular spectra, not atomic spectra - it is thus more common to speak of the movement of the peaks in the spectrum rather than lines.
\Delta\lambda = \lambda\!_{\text{state 1} \atop \text{observed}} - \, \lambda\!_{\text{state 2} \atop \text{observed}}
where \lambda is the wavelength of the spectral peak of interest and \lambda\!_{\text{state 1} \atop \text{observed}} > \, \lambda\!_{\text{state 2} \atop \text{observed}}\!.
For example, β-acylpyrrole will show a hypsochromic shift of 30-40 nm in comparison with α-acylpyrroles.
See also
- Bathochromic shift, a change in band position to a longer wavelength (lower frequency).
References
- ^ "Illustrated Glossary of Organic Chemistry - Bathochromic shift, hypsochromic shift; red shift; blue shift". www.chem.ucla.edu. Retrieved 2024-11-11.