Ultraviolet and Visible Spectroscopy

Absorption of electromagnetic radiation in the UV and visible regions of the spectrum results in…

excitation of outer shells

Give some key facts about UV spectroscopy.

What can UV / visible spectroscopy be applied to?

Atoms: Atomic orbitals : s, p, d etc

Molecules: Molecular orbitals: Sigma, pi,

Show how the electronic energy levels of a molecule of hydrogen change when goes from normal to excited state .

What electron transitions are possible?

Non-highlighted do occur but outside energy range

What are the UV selection rules?

* Simultaneous excitation of more than one electron is forbidden
* An electron must not change its spin during transition

Draw a digram to show molecular orbitals which may be involved in electronic transitions.

CHROMOPHORE:

= Is part of a molecule responsible for absorption in the accessible UV or visible region of the spectrum

→ Most of the time will be a %%benzene ring (aromatic)%% or could be %%extended conjugated system%%

AUXOCHROME:

= is a functional group that has no such absorption of its own but which modifies the absorption properties at a chromophore

What are the characteristics of UV/ visible spectra?

When is fluorescence spectroscopy used?

Will be used in the BP if a molecule is fluorescence

Relevant for biological systems

What are the characteristics of fluorescent compounds?

Fluorescence depends on…

rigidity of the molecule

Fluorescence differs from absorbance in that…

What are the sources of quenching?

What are the advantages of fluorescence spectroscopy?

What applications of fluorescence spectroscopy?

What are the different fluorescent markers you can have?

* Enzyme -specific
* DNA specific
* Calcium specific