Why is the Stokes shift important?
The presence of appreciable Stokes shift is principally important for practical applications of fluorescence because it allows to separate (strong) excitation light from (weak) emitted fluorescence using appropriate optics.
Why does a large Stokes shift indicate a large change in geometry between the ground and excited states?
A large stokes shift may indicate a fast relaxation from the initial state to the emissive state, could also be due to intramolecular energy-transfer (part of the molecule acts as a donor, absorbing light and another portion of the molecule acts as an acceptor, which emits light with a significant red shift).
How is Stokes shift measured?
Most recent answer
- Stokes shift usually calculates in wavenumber (unit = cm-1).
- Convert to wavelength (nm) to wavenumber (cm-1) [for that, abs 307 nm = 107/307 cm-1 = 32573.29 cm-1 , emi 469 nm = 107/469 cm-1 = 21321.96 cm-1 ,]
- Stokes shift = Absorption (wavenumber) – Emission(wavenumber)
What are Stokes and anti Stokes lines explain it?
Stokes lines are of longer wavelength than that of the exciting radiation responsible for the fluorescence or Raman effect. Thus, anti-Stokes lines are always of shorter wavelength than that of the light that produces them.
What do you mean by Bathochromic shift?
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).
Under what conditions can a Stokes shift occur in atomic spectroscopy?
Stoke’s shift can occur in atomic spectroscopy when an electron is excited to a high energy electronic level emits a photon and relaxes to a lower excited electronic level, the emitted radiation (solid line) has lower energy, and thus longer wavelength. s; the lifetime of the excited state (for emission lines).
What is the difference between Stokes and Anti-Stokes lines?
Stokes lines are of longer wavelength than that of the exciting radiation responsible for the fluorescence or Raman effect. Anti-Stokes lines are found in fluorescence and in Raman spectra when the atoms or molecules of the material are already in an excited state (as when at high temperature).
What is the Hypochromic effect?
The Hypochromic Effect describes the decrease in the absorbance of ultraviolet light in a double stranded DNA compared to its single stranded counterpart. It also absorbs more ultraviolet light since the bases no longer forms hydrogens bonds and therefore are free to absorb light.
What is auxochrome example?
Any portion of a molecule, i.e. radical or ionic functional group, that improves the color of the chromophore in an organic colorant. Auxochromes can also provide an ionic site that enables the dye to bind to a fiber. Examples of auxochrome groups are -COOH, -SO3H, -OH, and -NH3.
What is Stokes and anti Stoke’s lines?
Anti-Stokes lines are found in fluorescence and in Raman spectra when the atoms or molecules of the material are already in an excited state (as when at high temperature). In this case the radiated line energy is the sum of the pre-excitation energy and the energy absorbed from the exciting radiation.