Activity 10 | Emission Spectroscopy

Spectroscopy

The study of the interaction of light (electromagnetic radiation) with matter, including measurements of the absorbance, transmission, emission, reflection, and/or scattering light

Luminescent molecule/luminophore

A molecule that is luminescent (emits light)

Emission spectroscopy

A technique that measures which wavelengths of light are emitted by a sample, and sometimes also how much of each wavelength of light is emitted

Emission spectrometer

The sample emits the wavelengths of light that correspond to its energy levels, which are separated into the component wavelengths by a wavelength selector. The emitted wavelengths of light are detected, and the output can be displayed as a plot of emission intensity vs. wavelength of light

Emission spectrum

A plot of intensity of the emitted light vs. wavelength of emitted light. Can be continuous for a given range of wavelengths, meaning that some amount of every wavelength in a certain range is emitted by the sample. Can also be noncontinuous, or a line spectrum, having a region within the wavelength range where there is no light emitted

Intercalation

A mode of DNA binding where the small molecule inserts itself between the base pairs in the double helical structure of the DNA, lengthening and unwinding the double helical structure in the process

Indicator

Any molecule that can show (or indicates) the presence of another chemical substance via a physically observable change

“turn on” indicator

Indicator is unable to luminesce (emit light) on its own, but once intercalated into DNA, it becomes luminescent and emits light

“turn off” indicator

Is luminescent (emits light) on its own, but once intercalated into DNA, it can no longer luminesce (emit light)

DNA indicator

Indicates the presence or absence of DNA based on their changes in emission properties

Compact fluorescent lamp (CFL)

Coated on the inside with a fluorescent material, referred to as a phosphor, which can emit visible light when it transitions from an excited state to a lower energy state

Light emitting diode (LED)

Contain a solid-state material that emits a single color (wavelength) of visible light when a current passes through it

Emission Spectra of Metal Ions

Heat is usually used rather than electrical current. As the metal ions transition back to a lower energy state, they emit visible light

An atom or molecule emits light:

when a transition from a higher energy level to a lower energy level occurs

The wavelengths of light emitted by an atom:

are identical to those absorbed by that atom