New diagram lines in the L-emission spectrum of erbium-68

PHYSICS

Volume 24A, number 1

NEW

DIAGRAM

LINES

IN

THE

LETTERS

L-EMISSION

2 January 1967

SPECTRUM

OF

ERBIUM-68

A. N. NIGAM and Q. S. KAPOOR Physics

Department,

University

of Rajasthan,

Jaipur,

India

Received 2 December 1966

The L-emission spectrum of erbium has been investigated using a 40-cm curved mica crystal spectrograph of the transmission type. Four new diagram lines at 1344.2, 1666.3, 1640.8 and 1331.5 X.U. corresponding respectively to the dipole transition LuOI (78). quadrupole transition LIIMIII @I7) and forbidden transitions LIMI and LINI have been reported for the first time.

The L-emission spectrum of erbium has so far been studied by Coster [l], Wennerlof [2] and Sakellaridis [3]. Their data reveal the presence of two quadrupole lines pg (LIMv) and 610 (LIMIV) and all the dipole lines excepting r8 (LIIOI). With a view to recording the hitherto unobserved lines, we have reinvestigated the L-spectrum of erbium and we report the results of our studies in this paper. The experimental set up used to record the erbium spectrum was similar to the one described elsewhere [4]. A 40-cm curved mica crystal spectrograph of the transmission type was used. First order reflections from (100) and (201) planes giving a dispersion of about 12 X.U. per mm were employed. The exposures times ranged from 2 to 40 hours with the demountable X-ray tube operating at 20-30kV(full wave rectified), 3-4 mA. The erbium anticathode was prepared by embedding spec-pure erbium oxide powder (supplied by Johnson Matthey and Co., London) into properly machined grooves on one of the four faces of the massive copper anticathode. The present investigation has revealed, for the first time, the presence of four new diagram lines at 1344.2, 1666.3, 1640.8 and 1331.5 X.U. in the L-spectrum of erbium (table 1). The first corresponds to the dipole transition LIIOI (~8) and the second to the quadrupole transition LIIMIII (617). The last two have been assigned to the forbidden transitions LIMI and LlNI respectively. Our measured values of the wavelengths

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62

Table 1 Data for the new diagram lines in the L-spectrum bium-68. Transition

LII OI

LII MIII LI MI LI NI

Notation

Y8 PI 7

Nature

dipole quadrupole forbidden forbidden

Wavelength measured in X.U. 1344.2 1666.3 1640.8 1331.5

of er-

V/R value Obs.

1Calc.*

678.2 677.73 547.1 549.03 555.6 555.2 648.7 685.3

* For calculating these values, the v/R values of the energy levels as given by Sandstrijm [5] have been used.

are in good agreement with those calculated from energy levels [5] and give good fit with the Moseley plots. All the possible interferences with the newly observed lines have been taken into account and hence the existence of these lines in the L-spectrum of erbium has been conclusively established

References 1. D. Coster, Phil. Mag. 44 (1922) 546. 2. I. Wennerliif, Arkiv. Mat. Ast. Fys. 22A Nr. 8. 3. P. Sakellaridis, Compt. rend. 238 (1954) 4. A. N. Nigam, K. B. Garg and Q. S.Kapoor, of Phys. Sot. (London) to be published. 5. A. E. Sandstram, Handbuch der Physik 30 224, 226.

(1930) 2296. Proc. (1957)