- Email: [email protected]
The quadrupole transition LIMV (β9) in 65terbium
Volume 2, number 2
THE
June 1968
CHEMICAL PHYSICS LETTERS
QUADRUPOLE
TRANSITXON
Lf
MV
(69)
IN
65TERBiUM
A. N.NIGA.MandK. B.GARG Physics Department, University of Rajasthan, Jaipur. India Received 1’7 May 1968
Using a 40-cm curved mica crystal spectrograph of the transmission type, a new diagram line at X = 1656.41 XU corresponding to the quadrupole transition LI% (&) in terbium ‘has been reported for the first time. The line corresponding to the quadrupole transition LIMV @9) has been reported in the spectra
of almost all the elements from 2 = 46 to 2 = 92. In the rare-earth group of elements also it has been reported in the spectra of all except promethium, terbium and holmium. In this paper we report, for the first time, the existence of this line L 89 in terbium at X = 1656.41 XU. The experimental set up employed for the present study was exactly similar to the one employed for our earlier studies on terbium [1,2] and fully described elsewhere [3]. A 40-cm curved mica crystal spectrograph of the transmission type has been used to record the spectrum. In our earlier studies on terbium [1,2] we had employed only the first order reflections from the (100) and (201) sets of planes belonging to the (010) zone of muscovite mica. These yielded a dispersion of about 11.8 to 12 XU/mm only which was found insufficient to record the L p9 as a separate and independent line. For the present study, therefore, use has been made of the second order reflections from (201) and the first order reflections from (303) planes, giving a dispersion of about 5.6 XU/mm. The exposure time has been varied from 20 to 55 hours with the demountable X-ray tube operating at 30 KV;5mA (full wave rectified). The wavelength of the TbL pg line, as calculated from energy levels 143, comes out to be about 1657 XU, which is very close to that of the weak dipole line TbL p7, reported at h = 1655.1 XU. In all our terbium spectrograms recorded with the (100) and (201) planes reflecting in the first order, there always appeared a rather broad line centred at a wavelength of about 1656 XU which is about half way between the wavelengths of the TbL p 7 and TbL .8g lines. The intensity of this broad line was also found to be rather unusually large for either of the above two lines. A
possible explanation for this could be that these two lines had probably merged together for want of dispersion. In order to test this hypothesis we recorded the spectrum in the second order of the (201) planes which gave a dispersion of about 5.6 XU/mm. In these spectrograms we found that the broad line splits up into two weak, separate and distinct lines whose measured values of wavelengths match very well with those of the Tb L p 7 and TbLp9 lines. With a view to confirming the presence of the line TbL pg we recorded this spectrum in the first order of highly dispersive (403) planes (dispersion 5.6 Xv/mm) also and found this line to be unmistakably present. A survey of the wavelength tables [5,6] shcws that there are three lines HoL 84 (A = 1656.1 XU), NiKor l (X = 1654.51 XV) and NiK (r2 (h = 1658.34 XV) which are close to the line which has been assigned to TbL /39_ The interference due to the HoL p4 line can be completely ruled out on the ground that the other stronger lines of the Lspectrum of holmium are nowhere to be seen on any of these spectrograms. That the line observed at 1655.41 XU is due neither to NiK @yenor to NiK a2, ifat all present, can be seen from the following arguments_ Each of the two Ni lfnes is at about 1.9 XU from the new Line and since we have resolved TbL p7 (1655.1 XV) from the new line (difference 4X = 1.31 XU) the new line could not be due to either of the nickel lines. E’urther there is no chance of our making an error in measurement of the order of 1.9 XU. The wavelength of this newly observed line was measured by us taking the TbL ,G2 15 (k = = 1679.48 XV) and the TbL y5 (X = 1575.41 XV) as reference lines. The measured value of its wavelength which is the mean of a large number of separate and independent measurements comes out to be 1656.41 XU which is in good agreement with the calculated value. MOFeOVer, it was found 121
Volume 2, number 2
CHEMlCAL PHYSICS LETT.ERS
to fit nicely in the Bohr-Caster diagram. The existence of the line pg corresponding to the quadrupole transition L$+ in terbium may; therefore, be taken to have been established conclusively.
[l]
122
A. N. Nigam
[2] A.N. Nigam and K. B. Garg, Naturwiss., in press. [3] A. N. Nigam. K. B. Garg and Q.S. Kapoor. Proc. Phys.Soc. (London), in press. [4] -4:E.Sandstrom, Handbuchder Physik, Vol. 30 (1967) D. 224. [S] kid..‘;. 174. [S] J. A. Bearden, X-ray wavelengths. crgy Commission (1964).
References and K. B. Garg,
Naturwiss.
24 (1967) 641.
June 1968
U.S. Atomic
En-
THE
June 1968
CHEMICAL PHYSICS LETTERS
QUADRUPOLE
TRANSITXON
Lf
MV
(69)
IN
65TERBiUM
A. N.NIGA.MandK. B.GARG Physics Department, University of Rajasthan, Jaipur. India Received 1’7 May 1968
Using a 40-cm curved mica crystal spectrograph of the transmission type, a new diagram line at X = 1656.41 XU corresponding to the quadrupole transition LI% (&) in terbium ‘has been reported for the first time. The line corresponding to the quadrupole transition LIMV @9) has been reported in the spectra
of almost all the elements from 2 = 46 to 2 = 92. In the rare-earth group of elements also it has been reported in the spectra of all except promethium, terbium and holmium. In this paper we report, for the first time, the existence of this line L 89 in terbium at X = 1656.41 XU. The experimental set up employed for the present study was exactly similar to the one employed for our earlier studies on terbium [1,2] and fully described elsewhere [3]. A 40-cm curved mica crystal spectrograph of the transmission type has been used to record the spectrum. In our earlier studies on terbium [1,2] we had employed only the first order reflections from the (100) and (201) sets of planes belonging to the (010) zone of muscovite mica. These yielded a dispersion of about 11.8 to 12 XU/mm only which was found insufficient to record the L p9 as a separate and independent line. For the present study, therefore, use has been made of the second order reflections from (201) and the first order reflections from (303) planes, giving a dispersion of about 5.6 XU/mm. The exposure time has been varied from 20 to 55 hours with the demountable X-ray tube operating at 30 KV;5mA (full wave rectified). The wavelength of the TbL pg line, as calculated from energy levels 143, comes out to be about 1657 XU, which is very close to that of the weak dipole line TbL p7, reported at h = 1655.1 XU. In all our terbium spectrograms recorded with the (100) and (201) planes reflecting in the first order, there always appeared a rather broad line centred at a wavelength of about 1656 XU which is about half way between the wavelengths of the TbL p 7 and TbL .8g lines. The intensity of this broad line was also found to be rather unusually large for either of the above two lines. A
possible explanation for this could be that these two lines had probably merged together for want of dispersion. In order to test this hypothesis we recorded the spectrum in the second order of the (201) planes which gave a dispersion of about 5.6 XU/mm. In these spectrograms we found that the broad line splits up into two weak, separate and distinct lines whose measured values of wavelengths match very well with those of the Tb L p 7 and TbLp9 lines. With a view to confirming the presence of the line TbL pg we recorded this spectrum in the first order of highly dispersive (403) planes (dispersion 5.6 Xv/mm) also and found this line to be unmistakably present. A survey of the wavelength tables [5,6] shcws that there are three lines HoL 84 (A = 1656.1 XU), NiKor l (X = 1654.51 XV) and NiK (r2 (h = 1658.34 XV) which are close to the line which has been assigned to TbL /39_ The interference due to the HoL p4 line can be completely ruled out on the ground that the other stronger lines of the Lspectrum of holmium are nowhere to be seen on any of these spectrograms. That the line observed at 1655.41 XU is due neither to NiK @yenor to NiK a2, ifat all present, can be seen from the following arguments_ Each of the two Ni lfnes is at about 1.9 XU from the new Line and since we have resolved TbL p7 (1655.1 XV) from the new line (difference 4X = 1.31 XU) the new line could not be due to either of the nickel lines. E’urther there is no chance of our making an error in measurement of the order of 1.9 XU. The wavelength of this newly observed line was measured by us taking the TbL ,G2 15 (k = = 1679.48 XV) and the TbL y5 (X = 1575.41 XV) as reference lines. The measured value of its wavelength which is the mean of a large number of separate and independent measurements comes out to be 1656.41 XU which is in good agreement with the calculated value. MOFeOVer, it was found 121
Volume 2, number 2
CHEMlCAL PHYSICS LETT.ERS
to fit nicely in the Bohr-Caster diagram. The existence of the line pg corresponding to the quadrupole transition L$+ in terbium may; therefore, be taken to have been established conclusively.
[l]
122
A. N. Nigam
[2] A.N. Nigam and K. B. Garg, Naturwiss., in press. [3] A. N. Nigam. K. B. Garg and Q.S. Kapoor. Proc. Phys.Soc. (London), in press. [4] -4:E.Sandstrom, Handbuchder Physik, Vol. 30 (1967) D. 224. [S] kid..‘;. 174. [S] J. A. Bearden, X-ray wavelengths. crgy Commission (1964).
References and K. B. Garg,
Naturwiss.
24 (1967) 641.
June 1968
U.S. Atomic
En-