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Interferometrically Measured Thorium Wavelengths*

A. G I A C C H E T T I . † M . G A L L Λ R D O , M . J . G A R A V A G L I A , Z . G O N Z A L E Z , F . P . J . V A L E R O . ‡ AND E . Z A K O W I C Z

Departamenlo de Fisica, Universidad Nacional de La Plata, La Plata, Argentina

(Received 19 March 1964)

THE wavelengths of 129 thorium lines, excited in an electrode-less discharge lamp, have been measured interferometri­

cally. These lines may be divided into two groups.

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The first group includes 82 lines in the region 3400-4600 Å. The plates used for these measurements were taken by one of us (A.G.) during his stay at Purdue University, so all pertinent

details about the light source and the experimental method appear in the paper of Ref. 1. However it should be noted that in the measurements of the fractional order number ε= (D i

2)/[∆D2] a

TABLE I. Interferometrically measured thorium wavelengths.

corrected value for D02 was used here. First a corrected value

[∆D2] was obtained as explained in Ref. 1. Then the Di2 were

expressed as a function of D02. and [∆D2] in the following manner:

D02 = Di

2-i[∆D2]. A statistical weighting of this formula gives for D0

2 (for this case in which we measured six ring diameters):

The average deviation of these measurements is 3×10-4 A. For most of these lines this is the third independent interferometric measurement.

The second group includes 47 lines in the region 2680-3280 Å; this list may be considered an extension of that published by Davison, Giacchetti and Stanley1; in effect, most of these lines have been measured previously only by Littlefield and Wood.2

Our measurements were made on the same plates that were used for Ref. 1. A comparison between our measurements and those of Littlefield and Wood shows the presence of a small systematic error; the average deviation is 7×10 - 4 Å; our measurements give the larger values. The line 2687 Å, for which the difference is seven times the average deviation, was not included in the calculation of the average deviation. , The first column of Table I contains the relative intensity as taken from the monograph of Zalubas.3 The directly measured vacuum wavelengths of the thorium lines are given in the second column. This is followed by the air wavelength computed from Edlen formula for the dispersion of air.4 The last column gives the total number of observations.

All calculations were done with the Ferranti Mercury com­puter of the Instituto de Cálculo de la Universidad de Buenos Aires.

The authors thank Dr. A. Rodriguez for his assistance in writing the program, and Dr. M. Sadosky and Dr. R. de Guber for facilitating our use of the computer.

* This work was partially supported by a grant from the National Science Foundation.

† Present address: Chemistry Division, Argonne National Laboratory, 9700 South Cass Avenue, Argonne, Illinois.

‡ Present address: Physics Department, University of California, Berkeley, California.

1 A. Davison, A. Giacchetti, and R. W. Stanley, J. Opt. Soc. Am. 52, 447 (1962).

2 T. A. Littlefield and W. A. Wood, cited in Transactions of the Inter­national Astronomical Union XIA, 97 (1962).

3 R. Zalubas, Natl. Bur. Std. (U.S.) Monograph 17, (June 1960). 4 B. Edlen, T. Opt. Soc. Am. 43, 339 (1953).

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