About twenty isotopes and six nuclear isomers ( excited states of an isotope ) of berkelium have been characterized with the atomic numbers ranging from 235 to 254.

If we take the simple molecular orbital description of the ground state and combine that function with the functions describing all possible excited states using unoccupied orbitals arising from the same set of atomic orbitals, we also reach the full configuration interaction wavefunction.

The decay times of this fluorescence are of the order of nanoseconds, since the duration of the light depends on the lifetime of the excited states of the fluorescent material, in this case anthracene or stilbene.

Hadrons have excited states known as resonances.

Each ground state hadron may have several excited states ; several hundreds of resonances have been observed in particle physics experiments.

While short strings have zero entropy, he could identify long highly excited string states with ordinary black holes.

Electronic band theory ( a branch of physics ) says that a charge will flow if states are available into which electrons can be excited.

In most lasers this medium consists of population of atoms which have been excited into such a state by means of an outside light source, or an electrical field which supplies energy for atoms to absorb and be transformed into their excited states.

The gain medium absorbs pump energy, which raises some electrons into higher-energy (" excited ") quantum states.

However, the popular description of light being " stopped " in these experiments refers only to light being stored in the excited states of atoms, then re-emitted at an arbitrary later time, as stimulated by a second laser pulse.

In physics, specifically statistical mechanics, a population inversion occurs when a system ( such as a group of atoms or molecules ) exists in a state with more members in an excited state than in lower energy states.

where N < sub > 2 </ sub >( 0 ) is the number of excited atoms at time t = 0, and τ < sub > 21 </ sub > is the lifetime of the transition between the two states.

Therefore, when the numbers of atoms in the ground and excited states are equal, the rate of stimulated emission is equal to the rate of absorption for a given radiation density.

Recall from the descriptions of absorption and stimulated emission above that the rates of these two processes are proportional to the number of atoms in the ground and excited states, N < sub > 1 </ sub > and N < sub > 2 </ sub >, respectively.

Radiationless transition between levels, such as between the excited S = 0 and S = 1 states, may proceed quickly enough to siphon off a portion of the S = 0 population before it spontaneously returns to the ground state.

* In reactions, quantum chemistry studies the ground state of individual atoms and molecules, the excited states, and the transition states that occur during chemical reactions.

In the end, particles are regarded as excited states of a field ( field quanta ).

Multilevel systems can be used as well, if they possess two states that can be effectively decoupled from the rest ( e. g., ground state and first excited state of a nonlinear oscillator ).

Electrons excited to the conduction band also leave behind electron holes, i. e. unoccupied states in the valence band.

Electrons at these states can be easily excited to the conduction band, becoming free electrons, at room temperature.

Atoms also have distinct x-ray spectra that are attributable to the excitation of inner shell electrons to excited states.

* Time-resolved spectroscopy measures the decay rate ( s ) of excited states using various spectroscopic methods.

When a small bias V is applied to the system, only electronic states very near the Fermi level, within eV ( a product of electron charge and voltage, not to be confused here with electronvolt unit ), are excited.

In 1923, Danish and Dutch scientists Christian Christiansen and Hendrik Anthony Kramers, in an analysis of formation of polymers, pointed out that such a chain reaction need not start with a molecule excited by light, but could also start with two molecules colliding violently in the traditional way classically previously proposed for initiation of chemical reactions, by van't Hoff.

Although the term phosphorescence is derived from phosphorus, the reaction that gives phosphorus its glow is properly called chemiluminescence ( glowing due to a cold chemical reaction ), not phosphorescence ( re-emitting light that previously fell onto a substance and excited it ).

This is possible because chemical bond formation can occur on a timescale faster than electronic transitions, and therefore can result in discrete products in excited electronic states.

Chemiluminescence differs from fluorescence in that the electronic excited state is derived from the product of a chemical reaction rather than the more typical way of creating electronic excited states, namely absorption.

In chemiluminescence, an excited state is created via a chemical reaction.

This phenomenon can also be observed in many lasing systems, wherein a large fraction of the system's atoms ( for chemical and gas lasers ) or electrons ( in semiconductor lasers ) are in excited states.

The absorbed wavelengths, energy transfer efficiency, and time before emission depend on both the fluorophore structure and its chemical environment, as the molecule in its excited state interacts with surrounding molecules.

Photobleaching occurs as the fluorescent molecules accumulate chemical damage from the electrons excited during fluorescence.

The dependence of the scattering on atomic species makes it possible to obtain information pertaining to the chemical coordination environment of the original absorbing ( centrally excited ) atom by analyzing these EXAFS data.

These methods can deal with extremely complex chemical situations and, if computing power permits, may be used to reliably calculate molecular ground-and excited states if all other methods fail.

Since emotional reactions in the higher vertebrates depend on individual experience and are aroused in man, in addition, by complex symbols, one would expect that the hypothalamus could be excited from the cortex.

In photochemical reactions, atoms and molecules absorb energy ( photons ) of the illumination light and convert into an excited state.

However, in plant tissues that carry on photosynthesis, carotenoids act to quench electronically excited chlorophyll produced by visible light in a process called non-photochemical quenching, in order to prevent reactions which would otherwise infere with photosynthesis at high light levels.

Such reactions can lead to the formation of triplet excited species, which release photons upon returning to a lower energy level in a process analogous to phosphorescence.

After nuclear reactions that result in an excited nucleus, the energy that must be radiated or otherwise removed as binding energy for a single nucleus may be in the form of electromagnetic waves, such as gamma radiation, or it may appear in the kinetic energy of an ejected particle, such as an electron, in internal conversion decay.

Some clock reactions such as Briggs – Rauscher and BZ using the tris ( bipyridine ) ruthenium ( II ) chloride as catalyst can be excited into self-organising activity through the influence of light.

In these reactions it is the arene that is excited.

The first electronic excited state of an alkene lack the π-bond, so that rotation about the C-C bond is rapid and the molecule engages in reactions not observed thermally.

The chain of reactions is initiated by a blue light photon, which excites the flavin mononucleotide ( FMN ) photosensitizer to the singlet excited state.

But when he told some of his friends, their excited reactions convinced Morse to take the part.

For the great majority of systems under study, in particular for excited states and processes such as molecular dissociation reactions, the fourth item is by far the most important.