Molecular Luminescence Spectroscopy Flashcards
Forms of Luminescence (8)
Radio
Electro
Thermo
Tribo
Sono
Photo
Chemi
Bio
Jablonski Diagram Components (6)
Vibrational Relaxation
Internal Conversion
Fluorescence
Phosphorescence
Intersystem Crossing
External Crossing
a molecule of analyte absorbs a photon and excites a species in a process called photo-excitation
photoluminescence
no excitation radiation source; molecules of analyte are excited via chemical reaction to give a species whose emission spectrum provides information for quali/quanti analyses
chemiluminescence
Nonradiative deactivation in Jablonski Diagram
Vibrational Relaxation
Internal Conversion
Intersystem Crossing
External Conversion
Radiative Deactivation in Jablonski Diagram
Fluorescence
Phosphorescence
collisions of excited state analyte molecules with other molecules lead to loss of excess vibrational energy
vibrational relaxation
molecule passes to a lower energy state, vibrational energy levels of two electronic states overlap and molecules pass from one electronic state to other
Internal conversion
Spin of electron is reversed leading to change from singlet to triplet state
Jntersystem Crossing
Interaction and energy transfer between the excited molecules and the solvent or other molecules
External Conversion
emission of a photon via a singlet to singlet transition
fluorescence
emission of a photon via a triplet to singlet transition
Phosphorescence
all electron spins are paired; no energy level splitting occurs when the molecule is exposed to EMF
singlet
unpaired and parallel electron spins; excited state is less energetic than the corresponding state
Triplet
no net magnetic field due to spin pairing; electrons are repelled by permanent magnetic fields
Diamagnetic
magnetic moment and attracted to a magnetic field
paramagnetic
Types of fluorescence (2)
Resonance Fluorescence
Non-Resonance Fluorescence
absorbed radiation is re-emitted without a change in frequency and wavelength
Resonance Fluorescence
molecular fluorescence bands are shifted to wavelengths that are longer than the resonance line
non-resonance fluorescence