News on fundamental reference data

0584-8547/89s3.00 + 0.00 MaxwellPergamonMacmillanplc

Spectrochimica Acta, Vol. 44B, No. 7, pp. 725-128, 1989 Printedin Great Britain.

News on F~d~ental

Reference Data

ALEXANDER SCHEELINE School of Chemical Sciences University of Illinois at Urbana-Champaign 1209 W. California St. 79 RAL Box 48 Urbana, IL 61801 BITNET: SCHEELINE@UIUCSCS (Received as camera-ready

copy:19 April1989)

column continues the description of the various Data Centers at the National Institute of Standards and Technology (NIST) relevant to analytical atomic spectroscopists. THIS

1. NIST Data Center on Atomic Transition Probabilities The Data Center on Atomic Transition Probabilities collects, catalogs, and evaluates data on transition probabilities and oscillator strengths of atoms and atomic ions in the gas phase, as well as radiative lifetimes of atomic and ionic levels. It publishes critical reviews and tables of critically evaluated data, as well as annotated bibliographies. It is a clea~ngho~e for info~ation on transition moments, and responds to user requests for data, literature references, and technical info~ation. Written queries should be directed to the Center at: National Institute of Standards and Technology, Building 221, Rm A 267, Gaithersburg, MD 20899. Director of the Center is WOLFGANG WIESE; routine contact should be via JEFFREY R. FUHR, phone (301) 975-3204.

Publications of data from the Center are available from a wide variety of sources. These addresses, as annotated in the list below, are: l

ACS:

American Chemical Society Distribution Office Room 210, 1155 Sixteenth St. NW, Washington, DC 20036,

l

ATP:

Data Center on Atomic Transition Probabilities, as listed above.

l

CRC

CRC Press, Boca Raton, FL 33431.

l

GPO:

Superintendent of Documents, U. S. Government Printing Office, Washington, DC 20402.

l

NTIS: National Technical Information Service, U.S. Department of Commerce, 5285 Port Royal Rd., Springfield, VA 22 161. Publications include:

PI J.R. Fuhr, G.A. Martin, and W.L. Wiese, “Atomic Transition Probabilities - Iron Through Nickel”, J, Phys. Chem. Ref. Data 17, Suppl, 4 (1988). (ACS)

PI G.A. Martin, J.R. Fuhr, and W-L. Wiese, “Atomic Transition Probabilities Scandium Through Manganese”, J. Phys. Chem. Re$ (ACS) 725

Data 17, Suppl. 3 (1988).

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News on fundamental reference data

[31 W.L. Wiese and G.A. Martin, “Atomic Transition

Probabilities”, CRC Handbook of Chemistry and Physics, 63rd Edition, E334. CRC Press, Boca Raton, FL (1982). (CRC)

[41 J.R. Fuhr, G.A. Martin,

W.L. Wiese, and S.M. Younger, “Atomic Transition Probabilities for Iron, Cobalt, and Nickel (A Critical Data Compilation of Allowed Lines)“, J. Phys. Chem. Ref. Data 10, 305 (1981). (ATP)

PI W.L. Wiese and G.A. Martin, “Wavelengths and Transition Probabilities

for Atoms and Atomic Ions”, Natl. Stand. Ref. Data Ser., Natl. Bur. Stand (U.S.) 68, Part II, “Transition Probabilities”. U.S. Government Printing Office, Washington, DC (1980). (GPO)

PI S.M. Younger, Probabilities Compilation

J.R. Fuhr, G.A. Martin, and W.L. Wiese, “Atomic Transition for Vanadium, Chromium, and Manganese (A Critical Data of Allowed Lines)“, J. Phys. Chem. Ref. Data 7, 495 (1978). (ATP)

171 G.A. Martin and W.L. Wiese, “Tables of Critically Evaluated Oscillator Strengths for the Lithium Isoelectronic

Sequence”, J. Phys. Chem. ReJ

Data 5, 537 (1976). (ATP)

PI W.L. Wiese and J.R. Fuhr, “Atomic Transition Titanium (A Critical Data Compilation Data 4, 263 (1975). (ATP)

Probabilities for Scandium and of Allowed Lines)“, J. Phys. Chem. Re$

PI M.W. Smith and W.L. Wiese, “Atomic Transition Probabilities of the Iron Group Elements (A Critical Data Compilation Phys. Chem. Ref. Data 2, 85 (1973). (ATP)

for Forbidden Lines for Selected Lines)“, J.

PO1 B.M. Miles and W.L. Wiese, “Critically Evaluated Transition

Probabilities for Ba I and II”, Natl. Bur Stand. (U.S.) Tech. Note 474. U.S. Government Printing Office, Washington, DC (1969); At. Data 1, 1 (1969). (ATP)

Ull W.L. Wiese, M.W. Smith, and B.M. Miles, “Atomic Transition

Probabilities (Na Through Ca - A Critical Data Compilation)“, Natl. Stand. Ref. Data Ser., Natl. Bur. Stand. (U.S.) 22, Vol. II. U.S. Government Printing Office, Washington, DC (1969). (NTIS)

WI W.L. Wiese, M.W. Smith, and B.M. Glennon, “Atomic Transition

Probabilities (H Through Ne - A Critical Data Compilation)“, Natl. Stand. Ref. Data Ser., Natl. Bur. Stand. (U.S.) 4, Vol. I. U.S. Government Printing Office, Washington, DC (1966). (ATP)

Bibliographies

include:

PI B.J. Miller, J.R. Fuhr, and G.A. Martin,

“Bibliography on Atomic Transition Probabilities (November 1977 Through March 1980)“, Natl. Bur. Stand, (U.S.), Spec. Publ. 505, Suppl. 1. U.S. Government Printing Oflice, Washington, DC (1980).

em

“Bibliography on Atomic Transition Probabilities (1914 Through October 1977)“, Natl. Bur. Stand, (U.S.), Spec. Publ. 505. U.S. Government Printing Of&e, Washington, DC (1978). (ATP)

PI J.R. Fuhr, B.J. Miller, and G.A. Martin,

One out of print item may be of interest, namely: [I] M.W. Smith and W.L. Wiese, “Graphical Presentation of Systematic Trends of Atomic Oscillator Strengths Along Isoelectronic Sequences and New Oscillator Strengths Derived by Interpolation”, Astrophys. J., Suppl. Ser. 23, No 196, 103 (1971).

News on fundamental reference data

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2. U~daies on Precious Colons

A publication from the NIST Atomic Energy Level Data Center listed as “in preparation” in the previous column [ Spectrochim. Acta 44B, 427 (198911 has now been published: [l] V. Kaufman and J. Sugar, “Wavelengths and Energy Level Classifications of Scandium Spectra for All Stages of Ionization,” J. Phys. Chem. Ref. Data 17, 1679 (1988). (ATP) The transition probability data on MO I obtained by WHALING and BRAULT using Mo(CO)s entrained in an ICP has now been published [l]. The editor apologizes for listing the wrong journal in the “in press” citation earlier (Ref. [5] in ~pec~r~ch~rn. Acta 44B, 129 (1989)). 3. Recent Reference

Data Pub~i~a~i~ns

The long-standing debate on the applicability of local thermal equilibrium models to behavior of analytical plasmas has seen additional discussion. A thorough study has been reported [2] in which electron, heavy particle, ionization, and excitation temperatures were independently determined. To obtain LTE-like behavior, a pressure above 5 atm and an electron concentration above 1023m-3 were required. Even at 10 atm, excitation of argon is apparently greater than would be anticipated at LTE or any of its variants. The authors suggest that transition probabilities for Ar I may be sufficiently in error to explain the disagreement between Ar excitation and LTE at high pressure. WIESE [3] has reviewed m~surements of Ar I transition probabi~ties, and also published new recommended values for these probabilities [4]. The new values are precise to (typi~lly) 10 percent. The values used by EDDY and coworker [2] were precise to 25 percent, and the new values fall within the error bounds for the older values. Inaccurate transition probabilities thus cannot explain the divergence of Ar emission intensity from generalized LTE as observed by EDDY. One must conclude that, even after electrons and heavy particles come into LTE, excitation is still out of equilibrium, and that kinetic or radiation transport factors are important in setting emission intensity. The idea that ICPs are non-equilibrium discharges is supported by EDDY’Swork.

A contrasting viewpoint has been suggested by FANNIN etal. (51. They presume that thermod~amics, rather than kinetics, dominate the distribution of population in the plasma. Furthe~ore, the plasma is regarded as a fluid with a distinct Fermi level. Taking into account the perturbation in chemical potential due to the finite size of the various atomic orbitals, they have fit the curved Boltzmann plot for a helium discharge at reduced pressure. Whether chemical potential can be predicted independent of level population measurements is unclear. No information on Ar is provided, but the approach taken is not species specific. This approach, in the editor’s opinion, is worthy of further study, as it allows for non-linear behavior within the context of equilibrium thermodynamics. If found to be an accurate model, additional corrections to transition probabilities determined in wall-stabilized arcs might be necessary. As presented to date, the values measured for chemical potential are related to presumed values for transition probabilities. Regardless of the outcome of the LTE discussions, one is left to doubt whether transition probabilities obtained in atmosphe~c pressure plasmas can be accurate, as level populations are not easily predictable. The WHALING and BRAULTmolybdenum transition probabilities [l] obtained from the ICP, while precise and consistent with an LTE interpretation, are at odds with much of the ICP literature and much of the atmospheric pressure plasma literature, as cited above. Recalling that MO was introduced into the ICP as a gaseous species, not requiring vaporization, the linearity of the Boltzmann plot may be due to a fortuitous compensation of conflicting factors, rather than to actual LTE [63.

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News on fundamental reference data

Transition moments for a few strong lines of Ag, Au, Ba, Cu, Sm, and Zr can be found in a paper by HANNAFORD and LOWE [III, as cited in a paper in Spectrochimicu Actu, Part B last year [8]. Additional data on Al, Ca, Cr, Fe, Ir, MO, Na, Vb, Pt, U, V, and Y can be found in an earlier paper by the same authors [9].

REFERENCES [l] W. Whaling and J.W. Brault, Phys. Ser. 38,707 (1989). [2] T.L. Eddy and Ahad Sedghinasab, IEEE Trans. Plasma Sci. 16,444 (1988). [3] W.L. Wiese, J. Quanf. Speclrosc. Radiat. Transfer 40,421 (1988). [4] W.L. Wiese, J.W. Bra&, K. Danzmann, V. Helbig, and M. Kock, Phys. Rev. A 39,246l (1989). [5] H.B. Fannin, J.J. Hurly, and F.R. Meeks, Appl. Spectrosc. 42, 1181 (1988). [6] J. Olcsik and E. J. Williamsen, Pittsburgh Conference on Analytical Chemistry and Applied Spectroscopy, Atlanta, GA, March, 1989, Paper 1109. [7] P. Hannaford and R.M. Lowe, Amt. J. Phys. 39, 829 (1986). [8] P. Hannaford and A. Walsh, Spectrochitn. Acta 43B, 1053 (1988). [9] P. Hannaford and R.M. Lowe, Opt. Eng. 22, 532 (1983).