Elements atomic transition probability

For the 2005 edition of this Handbook, we include new, more accurate data for Fe I and Fe II, and Ba I and Ba II The new tables contain critically evaluated atomic transition probabilities for over 10500 selected lines of all elements for which reliable data are available on an absolute scale. The material is largely for neutral and singly ionized spectra, but also includes a number of prominent lines of more highly charged ions of important elements. 

Two aspects should be emphasized in connection with the use of the analytical matrix elements. First, transition probabilities may readily be evaluated by solving related coupled equations, once the matrix elements are determined. The effort to integrate the coupled equations is significantly smaller than that to evaluate numerically the matrix elements. Second, in a model calculation the mechanisms involved in the ion-atom collision process are more evident than in a numerical calculation. This evidence may contribute significantly to the qualitative understanding of the vacancy exchange process. 

The pdf files in the Internet version of the Handbook mimic the new layout of the pages in the print edition. Furthermore, the number of interactive tables has been increased from 76 to 103. Among the topics included for the first time in interactive form are vapor pressure of the elements at high temperature heat of dilution and molar conductivity of acids electron and proton affinities atomic transition probabilities speed of sound in various media the NIST thermocouple tables and many others. The database from which these interactive tables are generated now has over 106,000 records which can be searched, manipulated, and displayed in a variety of ways. 

Most of the data are obtained from comprehensive compilations of the Data Center on Atomic Transition Probabilities at the National Institute of Standards and Technology. Specifically, data have been taken from recent critical compilations on H, He, and Li (Ref. 1) on Be and B (Ref. 2)j on neutral and singly-ionized C and N (Ref. 3) and on Na (Ref. 4), Mg (Ref. 4), Al (Ref. 5), and Si (Ref. 6). Material from earlier compilations for the elements H through Ne (Refs. 7 and 8) and Na through Ca (Ref. 9) was supplemented by some more recent material taken directly from the original literature. Most of the original literature is cited in the above tables and in recent bibliographies (Refs. 10 and 11) for lack of space, individual literature references are not cited here. 

Section 10 Atomic, Molecular, and Optical Physics Line Spectra of the Elements NIST Atomic Transition Probability Tables Electron Affinities... 

The first term on the right-hand side is a gain term due to transitions between level m and n, the second a loss term Nn is the number of atoms in level n. The important new element introduced by Einstein was the discovery of spontaneous emission. The transition probability is the sum of two contributions ... 

Since the transition probabilities of Fig. 14.6 are obtained numerically, it is not appreciably more difficult to include the diagonal matrix elements AA and l BB arising from the permanent dipole moments of the atomic states in the field. The... 

In these formulas the energy difference AE is measured in atomic units, transition probabilities are obtained in seconds and the submatrix element in the cases of one or two shells of equivalent electrons for LS coupling may be taken from (27.3) or (27.4). When calculating using intermediate coupling one has to bear in mind that the appropriate wave functions are of the form (11.10). 

In recent years, AES (2), ultraviolet photoelectron spectroscopy (20), and X-ray photoelectron spectroscopy (21a) have come to play prominent roles in studies analyzing the composition and bonding at surfaces. These techniques can conveniently be used to determine nondestructively the composition of the surface and changes of the surface composition under a variety of experimental conditions. Since the Auger transition probabilities are large, especially for elements of low atomic number, surface impurities in quantities as little as 1% of a monolayer ( 1013 atoms/cm2) may be detected. 

As Fig. 17.2 shows, the coverage of wavelength and transition probability data in the NIST ASD database becomes very incomplete for elements with atomic numbers Z > 29. The only spectra covered for these heavy elements are those of the neutral atom and those of up to four-times charged ions. For atomic energy levels the present coverage for heavy elements is even less. But among the heavier elements are several that are of considerable interest to fusion energy research, specifically Kr, Xe, Mo, Ta and W. We have compiled data... 

For long time the x-ray emission spectroscopy has been widely used to investigate electronic structures of materials. The x-ray emission spectrum is conventionally considered as a characteristic quantity of elements and most theoretical calculations of x-ray transition probabilities have so far been made for free atoms. 

Experimental studies on the K0/Ka x-ray intensity ratio for 3d elements have shown [18-23] that this ratio changes under influence of the chemical environment of the 3d atom. Brunner et al. [22] explained their experimental results due to the change in screening of 3p electrons by 3d valence electrons as well as the polarization effect. Band et al. [24] used the scattered-wave (SW) Xa MO method [25] and calculated the chemical effect on the K0/Ka ratios for 3d elements. They performed the SW-Xa MO calculations for different chemical compounds of Cr and Mn. The spherically averaged self-consistent-field (SCF) potential and the total charge of valence electrons in the central atom, obtained by the MO calculations, were used to solve the Dirac equation for the central atom and the x-ray transition probabilities were calculated. 

The elements of this matrix are interpreted as the transition probabilities of electrons of going from the ith atom to the j th atom at different time intervals. The diagonal elements are called self-retum probabilities by analogy with the —> sdf-retuming walks. 

Converting the absorption lines into abundances requires knowledge of line positions of neutral and ionized atoms, as well as their transition probabilities and lifetimes of the excited atomic states. In addition, a model of the solar atmosphere is needed. In the past years, atomic properties have seen many experimental updates, especially for the rare earth elements (see below). Older solar atmospheric models used local thermodynamic equilibrium (LTE) to describe the population of the quantum states of neutral and ionized atoms and molecules according to the Boltzmann and Saha equations. However, the ionization and excitation temperatures describing the state of the gas in a photospheric layer may not be identical as required for LTE. Models that include the deviations from LTE (=non-LTE) are used more frequently, and deviations from LTE are modeled by including treatments for radiative and collision processes (see, e.g., [27,28]). 

Rare earth elements In the past years, many improvements have been made in abundance analyses of the REE through measurements of atomic lifetimes and transition probabilities, notably by the Wisconsin group. A recent paper by [63] summarizes the efforts and gives abundances for the REE. Now the REE abundances are among the best-known abundances for the sun. The following lists several papers on REE that appeared since 2003 the new values for Ce, Dy, Tm, Yb, and Lu are from [63],... 

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