What is Franck-Condon principle?
The Franck-Condon principle states that electron rearrangements occur so rapidly that nuclei can be considered as stationary until the rearrangement is complete.
What is the principle of electronic spectroscopy?
In electron spectroscopy, depending on the technique, irradiating the sample with high-energy particles such as X-ray photons, electron beam electrons, or ultraviolet radiation photons, causes Auger electrons and photoelectrons to be emitted.
Which region is electronic spectra observed?
The energies associated with molecular electronic spectra (typically in the optical or uv region) are typically much larger than those associated with vibrational spectra (typically in the infrared) and rotational spectra (typically in the microwave region).
What is dissociation and Predissociation?
If excitation transfers a molecule in a state containing more energy than the separated components (atoms, or molecules), dissociation takes place. Above the dissociation limit the energy is not quantized and energy continuum appears instead of discrete energy levels.
How many types of spectroscopy are there?
There are many different types of spectroscopy, but the most common types used for chemical analysis include atomic spectroscopy, ultraviolet and visible spectroscopy, infrared spectroscopy, Raman spectroscopy and nuclear magnetic resonance.
What is transition in spectroscopy?
Molecular electronic transitions take place when electrons in a molecule are excited from one energy level to a higher energy level. The energy change associated with this transition provides information on the structure of a molecule and determines many molecular properties such as colour.
Why UV is also called electronic spectroscopy?
The energies noted above are sufficient to promote or excite a molecular electron to a higher energy orbital. Consequently, absorption spectroscopy carried out in this region is sometimes called “electronic spectroscopy”.
What is the range of electronic spectroscopy?
An absorption spectrometer works in a range from about 200 nm (in the near ultra-violet) to about 800 nm (in the very near infra-red). Only a limited number of the possible electron jumps absorb light in that region.
What is the difference between electronic transition and vibrational transition?
Molecular Spectra Electronic transitions are vertical or almost vertical lines on such a plot since the electronic transition occurs so rapidly that the internuclear distance can’t change much in the process. Vibrational transitions occur between different vibrational levels of the same electronic state.
What is meant by Predissociation?
Definition of predissociation : the transition without emission of radiation of a molecule from a stable excited state to an unstable excited state that leads to dissociation.