Bathochromic shift

Bathochromic shift is a change of spectral band position in the absorption, reflectance, transmittance, or emission spectrum of a molecule to a longer wavelength (lower frequency).

This 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 bathochromic shift. Bathochromic 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.

:$Deltalambda\; =\; lambda^\{mathrm\{state\; 2\_\{mathrm\{observed\; -\; lambda^\{mathrm\{state\; 1\_\{mathrm\{observed$ where $lambda$ is the wavelength of the spectral peak of interest and $lambda^\{mathrm\{state\; 2\_\{mathrm\{observed\; >\; lambda^\{mathrm\{state\; 1\_\{mathrm\{observed$

Bathochromic shift is typically demonstrated using a spectrophotometer, colorimeter, or spectroradiometer.

Although bathochromic shifts are often referred to as red shifts, this usage is considered informal [http://www.iupac.org/reports/1996/6812verhoeven/R.htm#redshift] , and has no relation to Doppler shift or other wavelength-independent meanings of redshift. This usage is often found in the scientific literature .

ee also

Hypsochromic shift, a change to shorter wavelength (higher frequency)