1 / 5

DIPHENYLPOLYENE DYE SPECTRA

DIPHENYLPOLYENE DYE SPECTRA. UV-VISIBLE SPECTROSCOPY PARTICLE IN THE BOX. QUANTUM MECHANICAL MODEL. Delocalized pi electrons in a conjugated dye molecule are constrained to move along the C-C backbone.

jaime-boyle
Download Presentation

DIPHENYLPOLYENE DYE SPECTRA

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. DIPHENYLPOLYENE DYE SPECTRA UV-VISIBLE SPECTROSCOPY PARTICLE IN THE BOX

  2. QUANTUM MECHANICAL MODEL • Delocalized pi electrons in a conjugated dye molecule are constrained to move along the C-C backbone. • What energy states are the pi electrons in? The particle in the box model provides the answer. • En = n2h2/8mL2 where L is the length of the dye molecule, m is the electron mass, h is Planck’s constant and n is 1,2 ,3…

  3. QM Model - 2 • Light absorbed by the dye molecule will cause the electron to be promoted from ni to nf. • The energy of this transition is ΔE = (nf2 -ni2)h2/8mL2 = hc/ • Measure the absorption spectra for three dye molecules (with increasing L values)

  4. BEER’S LAW • Beer’s Law describes the dependence of absorption intensity on dye molecule concentration, [J]. • A = ε [J]ℓ where ε is the molar absorption coefficient and ℓ is the cell path length. • A linear least analysis of A vs [J] yields ε.

  5. Analysis • Calculate the Particle in the Box predictions for absorption wavelength and compare them to the experimental values. • Modify the Box model using a factor α. • Use the absorbance vs dye concentration data to determine the extinction coefficient for one dye.

More Related