Excited state, of an atom

Excitation—The addition of energy to a system, thereby transferring it from its ground state to an excited state. Excitation of a nucleus, an atom, or a molecule can result from absorption of photons or from inelastic collisions with other particles. The excited state of an atom is an unstable or metastable state and will return to ground state by radiation of the excess energy. 

In order to avoid such ambiguities, the definition of chemical species will depend on the simple concept of stability. In the absence of chemical reactions, a chemical species will last indefinitely. Thus an ion is a distinct chemical species, and an electron transfer reaction must be seen as a chemical change. However, an electronic excited state of an atom or molecule must inevitably decay back to the ground state, so the processes of excitation, emission and non-radiative deactivation are photophysical processes. 

Obviously, the various electronically excited states of an atomic or molecular ion vary in their respective radiative lifetime, t. The probability distribution applicable to formation of such states is thus a function of the time that elapses following ionization. Ions in metastable states, which have no allowed transitions to the ground state, are most likely to contribute to ion-neutral interactions observed under any experimental conditions since these states have the longest lifetimes. In addition, the experimental time scale of a particular experiment may favor some states over others. In single-source experiments, short-lived excited states may be of greater relative importance than in ion-beam experiments, in which there is typically a time interval of a few microseconds between ion formation and the collision of that ion with a neutral species, so that most of the short-lived states will have decayed before collision. There are several recent compilations of lifetimes of excited ionic states.lh,20 ,2,... 

This aspect of the uncertainty principle, due originally to Bohr, refers to a measurement of the energy carried out during a time interval At. It implies that a short-lived excited state of an atom or molecule, for which A/ is small, will be associated with a relatively large uncertainty in energy E. This is one factor contributing to the broadening of spectral lines. 

Figure 1.6 Energy levels at ground state and excited state of an atom showing degenerates...

This results from collision of atoms with atoms of other species. The energy level of both the ground and excited states of an atom will be influenced by interaction with... 

On the Nonperturbative Solution of the TDSE for Problems Where a Ground or an Excited State of an Atom (Molecule) Interacts With a Strong Electromagnetic Pulse of Short Duration... 

ON THE NONPERTURBATIVE SOLUTION OF THE TDSE FOR PROBLEMS WHERE A GROUND ORAN EXCITED STATE OF AN ATOM (MOLECULE) INTERACTS WITH A STRONG ELECTROMAGNETIC PULSE OF SHORT DURATION... 

The radiationless decay of a quasidiscrete excited state of an atom or molecule into an ion and electron of the same total energy is called autoionization. The quasidiscrete state must, of course, lie above the first ionization potential of the atom or molecule. The occurrence of autoionization may be inferred from the appearance of absorption spectra or ionization cross-section curves which exhibit line or band structure similar to that expected for transitions between discrete states. However, in the case of autoionization the lines or bands are broadened in inverse proportion to the lifetime of the autoionizing state, as required by the uncertainty principle. In the simple case of one quasidiscrete state embedded in one continuum, the line profile has a characteristic asymmetry which has been shown to be due to wave-mechanical interference between the two channels, i.e., between autoionization and direct ionization. In an extreme case the line profile may appear as a window resonance, i.e., as a minimum in the absorption cross section. 

A metastable state is defined as an excited state of an atom which does not (according to the selection rules) combine with the ground state of the atom. For example, the (the lowest lying level of the helium triplet system) will not combine with the I Sq (ground) state of helium. Thus, the... 

The excited state of an atom or molecule has an intrinsic hfetime due to radiative decay, which is given by... 

What is the difference between the groxmd state of an atom and an excited state of an atom ... 

The transition of the sodium atom from the excited state 1s 2s 2p 3p to the ground state 1s 2s 2p 3s is accompanied by the emission of yeiiow iight at 589 nm. Excited states of an atom are needed to describe its spectrum. 

Core hole state Excited state of an atom in which an electron has been removed from one of the inner shells. 

Energy, potential The energy available due to position or condition. Example Excited state of an atom. 

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