Bathochromic shift
Encyclopedia
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
).
Because the red
color in the visible spectrum
has a higher wavelength than most other colors, this effect is also commonly called a red shift, although this usage is considered informal, and has no relation to Doppler shift or other wavelength-independent meanings of redshift
. This usage is often found in the scientific literature
.
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.
where 
is the wavelength of the spectral peak of interest and 
Bathochromic shift is typically demonstrated using a spectrophotometer, colorimeter
, or spectroradiometer
.
Transmittance
In optics and spectroscopy, transmittance is the fraction of incident light at a specified wavelength that passes through a sample. A related term is absorptance, or absorption factor, which is the fraction of radiation absorbed by a sample at a specified wavelength...
, or emission spectrum
Emission spectrum
The emission spectrum of a chemical element or chemical compound is the spectrum of frequencies of electromagnetic radiation emitted by the element's atoms or the compound's molecules when they are returned to a lower energy state....
of a molecule to a longer wavelength
Wavelength
In physics, the wavelength of a sinusoidal wave is the spatial period of the wave—the distance over which the wave's shape repeats.It is usually determined by considering the distance between consecutive corresponding points of the same phase, such as crests, troughs, or zero crossings, and is a...
(lower frequency
Frequency
Frequency is the number of occurrences of a repeating event per unit time. It is also referred to as temporal frequency.The period is the duration of one cycle in a repeating event, so the period is the reciprocal of the frequency...
).
Because the red
Red
Red is any of a number of similar colors evoked by light consisting predominantly of the longest wavelengths of light discernible by the human eye, in the wavelength range of roughly 630–740 nm. Longer wavelengths than this are called infrared , and cannot be seen by the naked eye...
color in the visible spectrum
Visible spectrum
The visible spectrum is the portion of the electromagnetic spectrum that is visible to the human eye. Electromagnetic radiation in this range of wavelengths is called visible light or simply light. A typical human eye will respond to wavelengths from about 390 to 750 nm. In terms of...
has a higher wavelength than most other colors, this effect is also commonly called a red shift, although this usage is considered informal, and has no relation to Doppler shift or other wavelength-independent meanings of redshift
Redshift
In physics , redshift happens when light seen coming from an object is proportionally increased in wavelength, or shifted to the red end of the spectrum...
. This usage is often found in the scientific literature
Scientific literature
Scientific literature comprises scientific publications that report original empirical and theoretical work in the natural and social sciences, and within a scientific field is often abbreviated as the literature. Academic publishing is the process of placing the results of one's research into the...
.
This can occur because of a change in environmental conditions: for example, a change in solvent polarity
Chemical polarity
In chemistry, polarity refers to a separation of electric charge leading to a molecule or its chemical groups having an electric dipole or multipole moment. Polar molecules interact through dipole–dipole intermolecular forces and hydrogen bonds. Molecular polarity is dependent on the difference in...
will result in solvatochromism
Solvatochromism
Solvatochromism is the ability of a chemical substance to change color due to a change in solvent polarity. Negative solvatochromism corresponds to hypsochromic shift with increasing solvent polarity and positive solvatochromism corresponds to bathochromic shift with increasing solvent polarity...
. 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 Bathochromic shift is typically demonstrated using a spectrophotometer, colorimeter
Colorimeter
For articles on Colorimeter see:* Colorimeter * Tristimulus colorimeter...
, or spectroradiometer
Spectroradiometer
Spectroradiometers are designed to measure the spectral power distributions of illuminants. They operate almost like spectrophotometers in the visible region...
.