Molecular Luminescence Spectrometry

Vocabulary flashcards covering key terms, mechanisms, instrumentation, and phenomena in Molecular Luminescence Spectrometry based on the lecture notes.

Molecular Luminescence Spectrometry

An analytical methodology concerned with the measurement of photons emitted by molecules after radiative excitation or as a result of a chemical reaction.

Photoluminescence

The emission of radiation that occurs following the absorption of photons, taking place when excited molecules return to the ground state through energy dissipation as radiation.

Chemiluminescence

The emission of light or radiation that is produced as a direct result of a chemical reaction.

Ground State of a Molecule

An electronic configuration wherein the outermost electrons are residing in the lowest available energy level.

Vibrational States

Energy states within an electronic energy level that are brought about by the vibration of atoms about a chemical bond.

Vibrational Relaxation

A fast non-radiative process (~$10^{-12}\,s$) by which upper vibrational levels lose energy and transition to the lowest vibrational level within a given electronic energy state.

Internal Conversion

A non-radiative process in which an excited electronic state couples to an upper vibrational level of a lower electronic energy state, followed by vibrational relaxation.

Intersystem Crossing

A non-radiative process where the lowest vibrational level of the first excited singlet state couples to an upper vibrational level of a triplet state.

Fluorescence

The emission of radiation arising from the transition of a molecule from the lowest vibrational level of an excited singlet state to the ground state, occurring within $10^{-10}$ to $10^{-6}\,s$.

Phosphorescence

The radiation emitted as a result of the deactivation of a molecule from the lowest vibrational level of an excited triplet state to the ground state, taking $10^{-5}$ to $10^{-6}\,s$.

Stoke's Shift

The phenomenon where the wavelength corresponding to fluorescence emission is longer than the wavelength of the excitation radiation source.

Heavy Atom Effect

An effect produced by halogen substituents on aromatic rings that favors intersystem crossing and lowers luminescence intensity.

Quantum Efficiency ($\Phi$)

The fraction of absorbed photons that is emitted as photoluminescence.

Inner Filter Effect

An effect at high analyte concentrations (absorbance greater than $2$) where emission intensity decreases because emitted radiation is re-absorbed by the solution.

Fluorometer

An instrument used for fluorescence measurement that employs optical filters as wavelength selectors.

Spectrofluorometer

An instrument used for fluorescence measurement that employs monochromator systems as wavelength selectors.

Excitation Spectrum

A spectrum obtained by measuring emission intensity at a fixed wavelength while varying the wavelength of the excitation radiation.

Emission Spectrum

A spectrum recorded by fixing the wavelength of excitation radiation and measuring the emission intensity across different wavelengths.

Synchronous Spectrum

A spectrum generated by simultaneously scanning the excitation and emission spectra at identical rates with a fixed wavelength difference.

Fluorogenic Reaction

A reaction in which an analyte reacts with a non-luminescent reagent to form a fluorescent product.