Bathochromic shift (from Greek βαθύς bathys, "deep"; and χρῶμα chrōma, "color"; hence less common alternate spelling "bathychromic") is a change of spectral band position in the absorption, reflectance, transmittance, or emission spectrum of a molecule to a longer wavelength (lower frequency). Because the red color in the visible spectrum has a longer wavelength than most other colors, the effect is also commonly called a red shift.
Hypsochromic shift is a change to shorter wavelength (higher frequency)
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.
- where is the wavelength of the spectral peak of interest and
- Kamlet, Mortimer J.; Taft, R. W. (1976). "The solvatochromic comparison method. I. The .beta.-scale of solvent hydrogen-bond acceptor (HBA) basicities". Journal of the American Chemical Society. 98 (2): 377–383. ISSN 0002-7863. doi:10.1021/ja00418a009.
- Buncel, Erwin; Rajagopal, Srinivasan (1990). "Solvatochromism and solvent polarity scales". Accounts of Chemical Research. 23 (7): 226–231. ISSN 0001-4842. doi:10.1021/ar00175a004.