Radiative lifetimes excited atoms

Natural Broadening The natural line width of an atomic spectral line is determined by the lifetime of the excited state and Heisenberg s uncertainty principle. The shorter the lifetime, the broader the line, and vice versa. Typical radiative lifetimes of atoms are on the order of 10 s, which leads to natural line widths on the order of 10 nm. 

Radiative lifetimes of atomic using pulsed dye and moleculav levels obtained laser excitation ... 

Lx>ng radiative lifetimes of metastable states support the high density of these particles in slightly ionized plasma, or in excited gas. Thus, according to Fugal and Pakhomov [18, 19] the density of metastable atoms of helium at pressure of the order of a few Torrs, at temperatures ranging from 4 to 300 K, is about two orders of magnitude above the density of electrons. The density of metastable atoms and molecules in... 

It can be seen from Table II that unless experimental conditions are carefully chosen, the contribution from emission to the over-all decay of X(np5 2Py2) can usually be neglected as more rapid kinetic processes result in the removal of the excited atoms. Further, as the mean radiative lifetime is long, it is possible to detect these atoms by absorption spectroscopy. (See Section VII.B, general kinetic equation for the removal of 2Pyt atoms.)... 

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 alkalilike behavior of metastable noble-gas atoms effectively transforms the excitation energy of the metastable noble-gas atom into electronic energy of a rare-gas halide molecule with large reaction cross section. Because the electronically excited noble-gas halides have short radiative lifetimes and the ground-state noble-gas halides are not strongly bound, the process of formation of electronically excited noble-gas halides from metastable noble-gas atoms has been shown to be ideal for the operation of the electronic transition laser and has been successfully used in high-efficiency rare-gas halide lasers in recent years.21"23... 

In any low angular momentum state the radiative decay rate is usually dominated by the high frequency transitions to low lying states, and as a result it is impossible to control completely the decay rate using a millimeter wave cavity. In a circular i = m = n - 1 state the only decay is the far infrared transition to the n — 1 level, and Hulet et al. have observed the suppression of the decay of this level.26 They produced a beam of Cs atoms in the circular n = 22, = m = 21 state by pulsed laser excitation and an adiabatic rapid passage technique.27 The beam of circular state atoms then passed between a pair of plates 6.4 cm wide, 12.7 cm long, spaced by 230.1 jum, and held at 6 K. The 0 K radiative lifetime is 460ps, and... 

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