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Isotope shift studies in the spectral lines of Yb I in the 3405–4365-Å region and term shifts of some odd- and even-parity energy levels
Spectrochimica Acta Part B 55 Ž2000. 197]202
Isotope shift studies in the spectral lines of Yb I in the ˚ region and term shifts of some odd- and 3405]4365-A even-parity energy levels S.M. Afzal, Pushpa M. Rao, S.A. AhmadU Spectroscopy Di¨ ision, Bhabha Atomic Research Centre, Mumbai 400 085, India Received 3 September 1999; accepted 7 December 1999
Abstract Isotope shifts, Ds Ž 172 Yb] 176 Yb., in 29 spectral lines of neutral ytterbium ŽYb I. are reported in the region ˚ Earlier measurements in this region are available for five lines. The present measurements of isotope 3405]4365 A. shift were carried out using the photoelectric recording Fabry]Perot spectrometer and highly enriched isotopic samples of 172 Yb and 176 Yb. Term isotope shifts, DT Ž 172 Yb] 176 Yb., have been evaluated for 19 even and five odd parity high lying energy levels of Yb I, and the configurations assigned to these levels are discussed. Q 2000 Elsevier Science B.V. All rights reserved. Keywords: Isotope shift; Term isotope shift; Energy levels of Yb I; Electronic configuration assignment
1. Introduction The first spectrum of ytterbium was initially studied by King w1x. Meggers and Scribner w2x reported wavelengths and relative intensities of ˚ 1668 spectral lines in the range of 2070]10 325 A.
U
Corresponding author. Department of Physics, Aligarh Muslim University, Aligarh, India. E-mail address: [email protected] ŽS.A. Ahmad.
They also identified four odd-parity levels belonging to 4f 14 6s6p and eight even-parity levels of 4f 14 6s 2 , 4f 14 6s ns Ž n s 7, 8. and 4f 14 6s nd Ž n s 5, 6. configurations. A detailed and up-to-date analysis of Yb I was published by Meggers and Tech w3x, which provided wavelengths and estimated intensities of 1791 lines of Yb I and they could classify 787 lines of Yb I as transitions between 102 even- and 77 odd-parity levels. The energy levels belonging to 4f 14 6s ns, 14 4f 6s nd and 4f 14 6s np configurations were first identified theoretically by Nir w4x. On the basis of
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S.M. Afzal et al. r Spectrochimica Acta Part B: Atomic Spectroscopy 55 (2000) 197]202
parametric calculations, Spector w5x identified the energy levels of 4f 13 5d6s 2 and 4f 13 6s 2 6p configurations. These assignments by Nir w4x and Spector w5x are included in Meggers and Tech w3x. Camus et al. w6x obtained even parity states with J s 0 and J s 2 belonging to the series 4f 14 6s ns Ž n s 13]62. 1 S 0 , 4f 14 6s nd Ž n s 11]64. 1 D 2 and 4f 14 6s nd Ž n s 11]21. 3 D 2 . Wyart and Camus w7x have extended the analysis and identified new 36 even- and 35 odd-parity levels of Yb I. A review of the historical development on isotope shift measurements in Yb I spectra is given in the work of Ahmad et al. w8x which covers studies up to 1980. Since then, various laser techniques have been employed for accurate measurements of isotope shifts in the spectral lines of w9x measured the Yb I. Behrens and Guthorline ¨ ˚ using Dopplerisotope shift in line at 5749.92 A free optogalvanic spectroscopy, and they found that their value of Ds Ž 172 Yb] 176 Yb. in this line deviated only by 3.6 MHz from our value w8x. Maier et al. w10x have reported isotope shifts in five Yb I transitions by using laser-induced fluorescence spectroscopy. Using Doppler-free twophoton laser spectroscopy, Kischkel et al. w11x have reported accurate values of isotope shifts of 4f 14 6s9d and 4f 14 6s10d levels of Yb I. The isotope values reported in Maier et al. w10x and Kischkel et al. w11x mostly agree with some of our earlier values w8x. van Wijngaarden and Li w12x have accurately measured the isotope shift and ˚ of Yb I by hyperfine splitting of the line 5556.6 A means of acousto-optic modulation method using a tunable dye laser. The present study was undertaken to measure the isotope shifts in the UV lines of Yb I and evaluate the term isotope shifts, DT Ž 172 Yb] 176 Yb., of the energy levels of Yb I and correlate these DT values with the assigned electronic configurations of these levels. DT values for 10 evenand five odd-parity levels of Yb I are being reported for the first time.
2. Experimental The isotope shift measurements in the ˚ region were carried out on a record3405]4365-A
ing Fabry]Perot spectrometer. The source being a liquid air-cooled hollow cathode discharge lamp which contained either a mixture of 172 Yb Ž97.2%. and 176 Yb Ž96.7%. in the ratio of 0.7:1.0 or a single isotope. The etalons used were coated for ˚ . and the visible the ultraviolet Ž l max s 3600 A ˚ . regions. Most of the lines were Ž l max s 4500 A recorded with single isotope in order to confirm the isotopic structure and also to measure the separation of close-by lines. The other experimental details are same as described in Afzal et al. w13x.
3. Results and discussions Isotope shift, Ds Ž 172 Yb] 176 Yb. whereafter referred to as ISx, has been measured in 29 lines ˚ ŽTable 1.. The of Yb I in the region 3405]4365A wavelengths of these lines and their classification in columns 1 and 2 are taken from Meggers and Tech w3x; three lines do not have any energy level ˚ 3488.855 classification. Eight lines at 3431.107 A, ˚ 3774.323 A, ˚ 4258.743 A, ˚ 4267.132 A, ˚ 4284.170 A, ˚ 4295.026 A ˚ and 4337.599 A ˚ Žlisted in Table 1. A, have been classified by Wyart and Camus w7x using the newly reported energy levels of Yb I. The values of isotope shift, Ds Ž 172 Yb] 176 Yb., are given in the last column in units of milliKayser Ž1 mKs 10y3 cmy1 .. The sign of isotope shift is according to the usual convention: it is positive if the heavier isotope lies on higher wavenumber side and vice versa. The accuracy of isotope shift is approximately 3 mK for Ds Ž 172 Yb] 176 Yb. G 50 mK. Ross and Miller w14x have reported an IS value ˚ whereas of y41.2 mK for the line at 3770.09 A, ˚ and the we got y51.9 mK. The line at 3770.095 A ˚ and 4149.06 A ˚ other two lines at 3872.85 A involve the common upper level at 43 805 cmy1 , and in the last two lines the measured IS values are y49.2 mK Žpresent work. and y50.2 mK w8x. These confirm our value of IS s y51.9 mK for ˚ and not y41.2 mK as the line at 3770.095 A reported by Ross and Miller w14x. For the line at ˚ our value of IS agrees with that of 3791.74 A, Ross and Miller w14x. Golovin and Striganov w15x ˚ line an IS value of have reported for 3464.37 A
S.M. Afzal et al. r Spectrochimica Acta Part B: Atomic Spectroscopy 55 (2000) 197]202
199
Table 1
˚ regiona Isotope shift, Ds Ž172 Yb] 176 Yb., in the spectral lines of Yb I in 3405]4365 A Wavelength ˚. ŽA 3406.200 3426.044 3431.107 3431.140 3452.398 3458.391 3460.269 3464.37 3488.855 3559.032 3578.561 3655.729 3699.514 3700.580 3734.694 3770.095 3774.323 3791.741 3798.402 3872.852 4125.538 4128.934 4258.743 4267.132 4284.170 4295.026 4333.909 4337.599 4361.639
Classification Odd level
Even level
17 992 ] 27 314 29 774 29 774 ] ] 28 857 19 710 17 992 19 710 17 992 17 288 25 859 17 992 17 288 25 859 17 992 17 992 17 992 23 188 48 701 48 745 48 761 48 699 25 068 25 068 25 068 23 188 47 409
47 341 ] 56 451b 58 911 58 732 ] ] 0 48 364 b 46 081 47 646 45 338 44 311 52 874 44 760 43 805 52 346 b 44 357 44 311 43 805 47 420 24 489 25 270 b 72 190 25 270 b 48 403 b 48 344 b 48 135 46 236 b 24 489
Ds Ž172 Yb] 176 Yb. ŽmK. c q61.3 y70 y97.7 y75.0 y80.3 y80.5 y73.8 q59.8 ;0 q51.6 ;0 q35 ;0 y84.4 y15 y51.9 y76.9 ;0 q10 y49.2 y152.0 q30 ;0 ;0 y15 y35 q25 q30 ;0
The wavelengths and classifications are taken from Meggers and Tech w3x. Classifications from Wyart and Camus w7x. c 1 mKs 10y3 cmy1 . a
b
q64.4 mK Žthis value is included in Table III of w14x., however, our IS value for this line is q59.8 ˚ has been classified as mK. The line at 4267.132 A Ž48 761]72 190. by Meggers and Tech w3x, whereas Wyart and Camus w7x have given the classification of this line as Ž48 699]25 279.. The observed isotope shift in this line is almost zero Žsee Section 3.2. which gives for the level at 48 699 cmy1 . DTf ŽXy 65. mK which supports the assignment of this level to 4f 14 6s9f w7x. 3.1. DT-Values of the high e¨ en parity energy le¨ els of Yb I We have evaluated the term isotope shift, DT
Ž 172 Yb] 176 Yb., of 19 even-parity levels of Yb I ŽTable 2. using the values of DT of low odd levels listed in Table 3, which have been taken from Ahmad et al. w8x. The energy levels and their J-values, designations and configurations are taken from Meggers and Tech w3x, but in some cases these have been taken from Wyart and Camus w7x Žsee footnote of Table 2.. DT-Values of eight even-parity levels are reported for the first time by us and are marked with ‘c’ in Table 2; for two levels DT values have been revised. Our earlier w8x DT values of ŽXy 117. mK and ŽXy 85. mK, respectively, for two levels at 43 805 cmy1 Ž J s 1. and 44 760 cmy1 Ž J s 2. belonging to 4f 14 6p 2 configuration have been confirmed in the
200
S.M. Afzal et al. r Spectrochimica Acta Part B: Atomic Spectroscopy 55 (2000) 197]202
present study. The level at 43 805 cmy1 is in˚ volved in the transition of the line at 3770.095 A and our measured value of IS in this line is y51.9 mK. The DT value for the level at 48 344 cmy1 Ž J s 0. belonging to 4f 14 6p 2 configuration, given in Ahmad et al. w8x has been now revised to ŽXy 67. mK. DT values for the levels belonging to 4f 14 6s7d and 4f 14 6s9d are in agreement with our earlier values. For the level at 48 403 cmy1
Ž J s 2. of 4f 14 6s10d configuration, the DT value has been revised to ŽXy 47. mK. The DT value of ŽXy 65. mK confirms the assignment of the level at 44 311 cmy1 Ž J s 1. to 4f 14 6s7d configuration. Presently evaluated DT values of ŽXy 13. mK, ŽXq 3. mK, ŽXy 15. mK and ŽXq 3. mK, respectively, for the levels at 46 081 cmy1 Ž J s 0., 52 346 cmy1 Ž J s 6., 56 451 cmy1 Ž J s 6. and 58 732 cmy1 Ž J s 4., confirm
Table 2 The term isotope shift, DT Ž172 Yb] 176 Yb., in the even-parity energy levels of Yb I a Energy levels Žcmy1 .
Designation
J
Configuration
DT Ž172 Yb] 176 Yb. ŽmK.
0.00 24 489.102 24 751.948 25 270.902 43 805.42 44 311.38 44 357.60 44 760.37 45 338.53 46 081.54 46 236.27d 47 341.82e 47 420.96 47 646.62g,h 48 135.60 48 344.42 48 364.89 d 48 403.40 52 346.97d 52 874.79 56 451.65d 58 732.06 58 911.39i,j
1
0 1 2 3 1 1 2 2 2 0 3 2 2 3 2 0 3 2 6 6 6 4 5
4f14 6s2 4f145d6s 4f145d6s 4f145d6s 4f14 6p2 4f14 6s7d 4f14 6s7d 4f14 6p2 4f13 5d6s6p 4f13 5d6s6p 4f13 6s2 6p Ž4f145d2 ?.,4f13 5d6s6p 4f14 6s9df 4f13 5d6s6p, 4f14 6s9d 4f13 5d6s6p 4f14 6p2 4f 14 6s10d 4f14 6s10d 4f13 5d6s6p 4f13 5d6s6p 4f13 5d6s6p 4f13 5d6s6p ]
Xb Xy 65b Xy 65b Xy 65b Xy 117 Xy 70c Xy 65 Xy 85 Xy 30 Xy 13c Xq 76c Xq 4 Xy 76 Xy 65c Xy 7 U Xy 67c c Xy 65 U Xy 47c c Xq 3 Xq 5 Xy 15c Xq 3c Xq 5c
S D 3 D 3 D 3 P 3 D 1 D 3 P Ž7r2,5r2. Ž7r2,7r2. Ž5r2,3r2. 3 F 1 f D Ž7r2,5r2. Ž7r2,3r2. 1 S 3 D 1 D 3
Ž7r2,5r2. ] Ž7r2,5r2. ]
a The values of the energy levels and their designations, J values and configurations are taken from Meggers and Tech w3x except for four levels Žmarked ‘d’. which are from Wyart and Camus w7x. b DT values taken from Ahmad et al. w8x. c New DT values from the present study. U Earlier DT values w8x revised. d These energy levels and their term, J values and configurations are from Wyart and Camus w7x. The level at 46236.27 cmy1 is also listed in Nir’s thesis w4x. e The level has been assigned to 4f 14 5d 2 in Meggers and Tech w3x, whereas indicated as doubtful in Martin et al. w16x and assigned to 4f 13 5d6s6p configuration in Wyart and Camus w7x and our DT value supports this. f The term and the configuration for this level are indicated as doubtful in Martin et al. w16x, but assigned to 1 D of 4f 14 6s9d in Wyart and Camus w7x. g The designation and the configuration for this level are not given in Martin et al. w16x. h Our DT value does not support its assignment to 4f 13 5d6s6p configuration as given in Meggers and Tech w3x. The configuration of this level is revised to 4f 14 6s9d in Wyart and Camus w7x and this is confirmed in the present study. i This level is listed as a new level in Wyart and Camus w7x but already reported in Meggers and Tech w3x. j 13 4f 5d6s6p configuration is suggested for this level.
S.M. Afzal et al. r Spectrochimica Acta Part B: Atomic Spectroscopy 55 (2000) 197]202
201
Table 3 The term isotope shift, DT Ž172 Yb] 176 Yb., in the odd-parity energy levels of Yb I a Energy levels Žcmy1 .
Designation
J
Configuration
DT Ž172 Yb] 176 Yb. ŽmK.
17 228.439 17 992.007 19 710.388 23 188.518 25 068.227 25 859.682 27 314.919 28 857.014 29 774.958 47 409.82 48 699.25e 48 701.60 48 745.40e
3
0 1 2 2 1 5 6 1 4 0 4 2 2
4f14 6s6p 4f14 6s6p 4f14 6s6p 4f13 5d6s2 4f14 6s6p 4f13 5d6s2 4f13 5d6s2 4f13 5d6s2 4f13 5d6s2 4f14 6s10p 4f14 6s9f 4f14 6s9ff 4f14 6s12p
Xy 65b Xy 65b Xy 65b Xq 76b Xy 32b Xq 80b Xq 83b Xq 57c Xq 80b Xy 65c Xy 65c Xy 65c Xy 65c
P P 3 P Ž7r2,3r2. 1 P Ž7r2,3r2. Ž7r2,5r2. Ž7r2,5r2. Ž7r2,5r2. 3 P,Ž1r2,1r2.d 3 F 3 f F 3 P 3
The values of the energy levels and their designations, J values and configurations are taken from Meggers and Tech w3x. DT values taken from Ahmad et al. w8x. c New DT values from the present study. d Designation for this level as given in Martin et al. w16x. e These levels are from Wyart and Camus w7x. f The level at 48701 cmy1 was unassigned in Meggers and Tech w3x and Martin et al. w16x, but assigned to 4f 14 6s9f in Wyart and Camus w7x which is confirmed presently. a
b
their assignment to 4f 13 5d6s6p configuration. For the level at 46 236 cmy1 Ž J s 3. of 4f 13 6s 2 6p, we have DTs ŽXq 76. mK which confirms the assignment. The term and assignment of the level at 47 420 cmy1 Ž J s 2. is given as 1 D Ž?. and 4f 14 6s9d Ž?. in Martin et al. w16x and present value of DTs ŽXy 76. mK confirms this assignment as indicated in Wyart and Camus w7x also. The level at 47 646 cmy1 has been assigned to 4f 13 5d6s6p in Maggers and Tech w3x but not in Martin et al. w16x and now the assignment has been revised to 4f 14 6s9d w7x, which is confirmed by our DT value of ŽXy 65. mK. The level at 47 646 cmy1 Ž J s 3. was assigned to 4f 13 5d6s6p configuration w16x but, our DT value of ŽXy 65. mK does not support this assignment, rather it supports the revised assignment of this level to 4f 14 6s9d w7x. DTs ŽX y 65. mK for the level at 48 364.89 cmy1 Ž J s 3. confirms its assignment to 4f 14 6s10d w7x. The unassigned level at 58 911 cmy1 Ž J s 5. has DTs ŽXq 5. mK which suggests 4f 13 5d6s6p configuration for this level. 3.2. DT-Values of the odd parity energy le¨ els of Yb I DT Ž 172 Yb] 176 Yb. for five odd parity levels
have been evaluated for the first time. The level at 28 857 cmy1 Ž J s 1., belonging to 4f 13 5d6s 2 configuration has DT value of ŽXq 57. mK. The DT value is low compared to other levels of 4f 13 5d6s 2 configuration having DT value around ŽXq 80. mK w8x. This level has been shown to have 48% Žf 7r2, d 5r2. and 22% Žf 5r2, d 3r2. by Nir w4x whereas Wyart and Camus w7x have assigned the leading component 3 P with 56% purity. The DT value of ŽXy 65. mK for both the levels at 47 409 cmy1 Ž J s 0. and 48 745 cmy1 Ž J s 2. confirm their assignments to f 14 sp configuration. For the level at 48 699 cmy1 Ž J s 4. of 4f 14 6s9f configuration, we have obtained DTs ŽX y 65. mK which confirms its assignment. The level at 48 701 cmy1 Ž J s 2. reported in Meggers and Tech w3x has been assigned to 4f 14 6s9f w7x and our value of DTs ŽXy 65. mK confirms this configuration assignment.
4. Conclusion Isotope shifts, involving isotopes 172 Yb and Yb, have been measured in few strong lines of Yb I in UV region. Term isotope shifts Ž DT. of the odd- and even-parity energy levels of Yb I 176
202
S.M. Afzal et al. r Spectrochimica Acta Part B: Atomic Spectroscopy 55 (2000) 197]202
reported earlier have been mostly confirmed. New DT values of 11 even- and five odd-parity levels have been reported and configuration assignments of these levels are discussed. References w1x A.S. King, Astrophys. J. 74 Ž1931. 328. w2x W.F. Meggers, B.F. Scribner, J. Res. NBS 19 Ž1937. 651]664. w3x W.F. Meggers, J.L. Tech, J. Res. NBS 88 Ž1978. 13]70. w4x S. Nir, Thesis, Hebrew University, Jerusalem Ž1969. 99]213 w5x N. Spector, J. Opt. Soc. Am. 61 Ž1971. 1350]1354. w6x P. Camus, A. Debarre, C. Morillon, J. Phys. B 11 Ž1978. L395. w7x J.F. Wyart, P. Camus, Phys. Scr. 20 Ž1979. 43]59. w8x S.A. Ahmad, I.J. Machado, G.D. Saksena, Spectrochim.
Acta Part B 35 Ž1980. 215]224. w9x H.-O. Behrens, G.H. Guthorlien, J. Phys. C7 Ž1983. ¨ 149]168. w10x J. Maier, C.S. Kischkel, M. Baumann, Z. Phys. D21 Ž1991. 145]151. w11x C.S. Kischkel, M. Baumann, E. Kummel, J. Phys. B25 Ž1992. 4447]4454. w12x W.A. van Wijngaarden, J. Li, J. Opt. Soc. Am. 11B Ž1994. 2163]2166. w13x S.M. Afzal, S.G. Nakhate, S.A. Ahmad, Z. Phys. D37 Ž1996. 249]253. w14x G.E. Miller, J.S. Ross, J. Opt. Soc. Am. 66 Ž1976. 585]589. w15x A.F. Golovin, A.R. Striganov, Opt. Spect. 9 Ž1965. 467]469. w16x W.C. Martin, R. Zalubas, L. Hagan, Atomic Energy Levels; The Rare Earth Elements, NSRDS-NBS 60, National Bureau of Standards, Washington, 1978.
Isotope shift studies in the spectral lines of Yb I in the ˚ region and term shifts of some odd- and 3405]4365-A even-parity energy levels S.M. Afzal, Pushpa M. Rao, S.A. AhmadU Spectroscopy Di¨ ision, Bhabha Atomic Research Centre, Mumbai 400 085, India Received 3 September 1999; accepted 7 December 1999
Abstract Isotope shifts, Ds Ž 172 Yb] 176 Yb., in 29 spectral lines of neutral ytterbium ŽYb I. are reported in the region ˚ Earlier measurements in this region are available for five lines. The present measurements of isotope 3405]4365 A. shift were carried out using the photoelectric recording Fabry]Perot spectrometer and highly enriched isotopic samples of 172 Yb and 176 Yb. Term isotope shifts, DT Ž 172 Yb] 176 Yb., have been evaluated for 19 even and five odd parity high lying energy levels of Yb I, and the configurations assigned to these levels are discussed. Q 2000 Elsevier Science B.V. All rights reserved. Keywords: Isotope shift; Term isotope shift; Energy levels of Yb I; Electronic configuration assignment
1. Introduction The first spectrum of ytterbium was initially studied by King w1x. Meggers and Scribner w2x reported wavelengths and relative intensities of ˚ 1668 spectral lines in the range of 2070]10 325 A.
U
Corresponding author. Department of Physics, Aligarh Muslim University, Aligarh, India. E-mail address: [email protected] ŽS.A. Ahmad.
They also identified four odd-parity levels belonging to 4f 14 6s6p and eight even-parity levels of 4f 14 6s 2 , 4f 14 6s ns Ž n s 7, 8. and 4f 14 6s nd Ž n s 5, 6. configurations. A detailed and up-to-date analysis of Yb I was published by Meggers and Tech w3x, which provided wavelengths and estimated intensities of 1791 lines of Yb I and they could classify 787 lines of Yb I as transitions between 102 even- and 77 odd-parity levels. The energy levels belonging to 4f 14 6s ns, 14 4f 6s nd and 4f 14 6s np configurations were first identified theoretically by Nir w4x. On the basis of
0584-8547r00r$ - see front matter Q 2000 Elsevier Science B.V. All rights reserved. PII: S 0 5 8 4 - 8 5 4 7 Ž 9 9 . 0 0 1 7 6 - 7
198
S.M. Afzal et al. r Spectrochimica Acta Part B: Atomic Spectroscopy 55 (2000) 197]202
parametric calculations, Spector w5x identified the energy levels of 4f 13 5d6s 2 and 4f 13 6s 2 6p configurations. These assignments by Nir w4x and Spector w5x are included in Meggers and Tech w3x. Camus et al. w6x obtained even parity states with J s 0 and J s 2 belonging to the series 4f 14 6s ns Ž n s 13]62. 1 S 0 , 4f 14 6s nd Ž n s 11]64. 1 D 2 and 4f 14 6s nd Ž n s 11]21. 3 D 2 . Wyart and Camus w7x have extended the analysis and identified new 36 even- and 35 odd-parity levels of Yb I. A review of the historical development on isotope shift measurements in Yb I spectra is given in the work of Ahmad et al. w8x which covers studies up to 1980. Since then, various laser techniques have been employed for accurate measurements of isotope shifts in the spectral lines of w9x measured the Yb I. Behrens and Guthorline ¨ ˚ using Dopplerisotope shift in line at 5749.92 A free optogalvanic spectroscopy, and they found that their value of Ds Ž 172 Yb] 176 Yb. in this line deviated only by 3.6 MHz from our value w8x. Maier et al. w10x have reported isotope shifts in five Yb I transitions by using laser-induced fluorescence spectroscopy. Using Doppler-free twophoton laser spectroscopy, Kischkel et al. w11x have reported accurate values of isotope shifts of 4f 14 6s9d and 4f 14 6s10d levels of Yb I. The isotope values reported in Maier et al. w10x and Kischkel et al. w11x mostly agree with some of our earlier values w8x. van Wijngaarden and Li w12x have accurately measured the isotope shift and ˚ of Yb I by hyperfine splitting of the line 5556.6 A means of acousto-optic modulation method using a tunable dye laser. The present study was undertaken to measure the isotope shifts in the UV lines of Yb I and evaluate the term isotope shifts, DT Ž 172 Yb] 176 Yb., of the energy levels of Yb I and correlate these DT values with the assigned electronic configurations of these levels. DT values for 10 evenand five odd-parity levels of Yb I are being reported for the first time.
2. Experimental The isotope shift measurements in the ˚ region were carried out on a record3405]4365-A
ing Fabry]Perot spectrometer. The source being a liquid air-cooled hollow cathode discharge lamp which contained either a mixture of 172 Yb Ž97.2%. and 176 Yb Ž96.7%. in the ratio of 0.7:1.0 or a single isotope. The etalons used were coated for ˚ . and the visible the ultraviolet Ž l max s 3600 A ˚ . regions. Most of the lines were Ž l max s 4500 A recorded with single isotope in order to confirm the isotopic structure and also to measure the separation of close-by lines. The other experimental details are same as described in Afzal et al. w13x.
3. Results and discussions Isotope shift, Ds Ž 172 Yb] 176 Yb. whereafter referred to as ISx, has been measured in 29 lines ˚ ŽTable 1.. The of Yb I in the region 3405]4365A wavelengths of these lines and their classification in columns 1 and 2 are taken from Meggers and Tech w3x; three lines do not have any energy level ˚ 3488.855 classification. Eight lines at 3431.107 A, ˚ 3774.323 A, ˚ 4258.743 A, ˚ 4267.132 A, ˚ 4284.170 A, ˚ 4295.026 A ˚ and 4337.599 A ˚ Žlisted in Table 1. A, have been classified by Wyart and Camus w7x using the newly reported energy levels of Yb I. The values of isotope shift, Ds Ž 172 Yb] 176 Yb., are given in the last column in units of milliKayser Ž1 mKs 10y3 cmy1 .. The sign of isotope shift is according to the usual convention: it is positive if the heavier isotope lies on higher wavenumber side and vice versa. The accuracy of isotope shift is approximately 3 mK for Ds Ž 172 Yb] 176 Yb. G 50 mK. Ross and Miller w14x have reported an IS value ˚ whereas of y41.2 mK for the line at 3770.09 A, ˚ and the we got y51.9 mK. The line at 3770.095 A ˚ and 4149.06 A ˚ other two lines at 3872.85 A involve the common upper level at 43 805 cmy1 , and in the last two lines the measured IS values are y49.2 mK Žpresent work. and y50.2 mK w8x. These confirm our value of IS s y51.9 mK for ˚ and not y41.2 mK as the line at 3770.095 A reported by Ross and Miller w14x. For the line at ˚ our value of IS agrees with that of 3791.74 A, Ross and Miller w14x. Golovin and Striganov w15x ˚ line an IS value of have reported for 3464.37 A
S.M. Afzal et al. r Spectrochimica Acta Part B: Atomic Spectroscopy 55 (2000) 197]202
199
Table 1
˚ regiona Isotope shift, Ds Ž172 Yb] 176 Yb., in the spectral lines of Yb I in 3405]4365 A Wavelength ˚. ŽA 3406.200 3426.044 3431.107 3431.140 3452.398 3458.391 3460.269 3464.37 3488.855 3559.032 3578.561 3655.729 3699.514 3700.580 3734.694 3770.095 3774.323 3791.741 3798.402 3872.852 4125.538 4128.934 4258.743 4267.132 4284.170 4295.026 4333.909 4337.599 4361.639
Classification Odd level
Even level
17 992 ] 27 314 29 774 29 774 ] ] 28 857 19 710 17 992 19 710 17 992 17 288 25 859 17 992 17 288 25 859 17 992 17 992 17 992 23 188 48 701 48 745 48 761 48 699 25 068 25 068 25 068 23 188 47 409
47 341 ] 56 451b 58 911 58 732 ] ] 0 48 364 b 46 081 47 646 45 338 44 311 52 874 44 760 43 805 52 346 b 44 357 44 311 43 805 47 420 24 489 25 270 b 72 190 25 270 b 48 403 b 48 344 b 48 135 46 236 b 24 489
Ds Ž172 Yb] 176 Yb. ŽmK. c q61.3 y70 y97.7 y75.0 y80.3 y80.5 y73.8 q59.8 ;0 q51.6 ;0 q35 ;0 y84.4 y15 y51.9 y76.9 ;0 q10 y49.2 y152.0 q30 ;0 ;0 y15 y35 q25 q30 ;0
The wavelengths and classifications are taken from Meggers and Tech w3x. Classifications from Wyart and Camus w7x. c 1 mKs 10y3 cmy1 . a
b
q64.4 mK Žthis value is included in Table III of w14x., however, our IS value for this line is q59.8 ˚ has been classified as mK. The line at 4267.132 A Ž48 761]72 190. by Meggers and Tech w3x, whereas Wyart and Camus w7x have given the classification of this line as Ž48 699]25 279.. The observed isotope shift in this line is almost zero Žsee Section 3.2. which gives for the level at 48 699 cmy1 . DTf ŽXy 65. mK which supports the assignment of this level to 4f 14 6s9f w7x. 3.1. DT-Values of the high e¨ en parity energy le¨ els of Yb I We have evaluated the term isotope shift, DT
Ž 172 Yb] 176 Yb., of 19 even-parity levels of Yb I ŽTable 2. using the values of DT of low odd levels listed in Table 3, which have been taken from Ahmad et al. w8x. The energy levels and their J-values, designations and configurations are taken from Meggers and Tech w3x, but in some cases these have been taken from Wyart and Camus w7x Žsee footnote of Table 2.. DT-Values of eight even-parity levels are reported for the first time by us and are marked with ‘c’ in Table 2; for two levels DT values have been revised. Our earlier w8x DT values of ŽXy 117. mK and ŽXy 85. mK, respectively, for two levels at 43 805 cmy1 Ž J s 1. and 44 760 cmy1 Ž J s 2. belonging to 4f 14 6p 2 configuration have been confirmed in the
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present study. The level at 43 805 cmy1 is in˚ volved in the transition of the line at 3770.095 A and our measured value of IS in this line is y51.9 mK. The DT value for the level at 48 344 cmy1 Ž J s 0. belonging to 4f 14 6p 2 configuration, given in Ahmad et al. w8x has been now revised to ŽXy 67. mK. DT values for the levels belonging to 4f 14 6s7d and 4f 14 6s9d are in agreement with our earlier values. For the level at 48 403 cmy1
Ž J s 2. of 4f 14 6s10d configuration, the DT value has been revised to ŽXy 47. mK. The DT value of ŽXy 65. mK confirms the assignment of the level at 44 311 cmy1 Ž J s 1. to 4f 14 6s7d configuration. Presently evaluated DT values of ŽXy 13. mK, ŽXq 3. mK, ŽXy 15. mK and ŽXq 3. mK, respectively, for the levels at 46 081 cmy1 Ž J s 0., 52 346 cmy1 Ž J s 6., 56 451 cmy1 Ž J s 6. and 58 732 cmy1 Ž J s 4., confirm
Table 2 The term isotope shift, DT Ž172 Yb] 176 Yb., in the even-parity energy levels of Yb I a Energy levels Žcmy1 .
Designation
J
Configuration
DT Ž172 Yb] 176 Yb. ŽmK.
0.00 24 489.102 24 751.948 25 270.902 43 805.42 44 311.38 44 357.60 44 760.37 45 338.53 46 081.54 46 236.27d 47 341.82e 47 420.96 47 646.62g,h 48 135.60 48 344.42 48 364.89 d 48 403.40 52 346.97d 52 874.79 56 451.65d 58 732.06 58 911.39i,j
1
0 1 2 3 1 1 2 2 2 0 3 2 2 3 2 0 3 2 6 6 6 4 5
4f14 6s2 4f145d6s 4f145d6s 4f145d6s 4f14 6p2 4f14 6s7d 4f14 6s7d 4f14 6p2 4f13 5d6s6p 4f13 5d6s6p 4f13 6s2 6p Ž4f145d2 ?.,4f13 5d6s6p 4f14 6s9df 4f13 5d6s6p, 4f14 6s9d 4f13 5d6s6p 4f14 6p2 4f 14 6s10d 4f14 6s10d 4f13 5d6s6p 4f13 5d6s6p 4f13 5d6s6p 4f13 5d6s6p ]
Xb Xy 65b Xy 65b Xy 65b Xy 117 Xy 70c Xy 65 Xy 85 Xy 30 Xy 13c Xq 76c Xq 4 Xy 76 Xy 65c Xy 7 U Xy 67c c Xy 65 U Xy 47c c Xq 3 Xq 5 Xy 15c Xq 3c Xq 5c
S D 3 D 3 D 3 P 3 D 1 D 3 P Ž7r2,5r2. Ž7r2,7r2. Ž5r2,3r2. 3 F 1 f D Ž7r2,5r2. Ž7r2,3r2. 1 S 3 D 1 D 3
Ž7r2,5r2. ] Ž7r2,5r2. ]
a The values of the energy levels and their designations, J values and configurations are taken from Meggers and Tech w3x except for four levels Žmarked ‘d’. which are from Wyart and Camus w7x. b DT values taken from Ahmad et al. w8x. c New DT values from the present study. U Earlier DT values w8x revised. d These energy levels and their term, J values and configurations are from Wyart and Camus w7x. The level at 46236.27 cmy1 is also listed in Nir’s thesis w4x. e The level has been assigned to 4f 14 5d 2 in Meggers and Tech w3x, whereas indicated as doubtful in Martin et al. w16x and assigned to 4f 13 5d6s6p configuration in Wyart and Camus w7x and our DT value supports this. f The term and the configuration for this level are indicated as doubtful in Martin et al. w16x, but assigned to 1 D of 4f 14 6s9d in Wyart and Camus w7x. g The designation and the configuration for this level are not given in Martin et al. w16x. h Our DT value does not support its assignment to 4f 13 5d6s6p configuration as given in Meggers and Tech w3x. The configuration of this level is revised to 4f 14 6s9d in Wyart and Camus w7x and this is confirmed in the present study. i This level is listed as a new level in Wyart and Camus w7x but already reported in Meggers and Tech w3x. j 13 4f 5d6s6p configuration is suggested for this level.
S.M. Afzal et al. r Spectrochimica Acta Part B: Atomic Spectroscopy 55 (2000) 197]202
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Table 3 The term isotope shift, DT Ž172 Yb] 176 Yb., in the odd-parity energy levels of Yb I a Energy levels Žcmy1 .
Designation
J
Configuration
DT Ž172 Yb] 176 Yb. ŽmK.
17 228.439 17 992.007 19 710.388 23 188.518 25 068.227 25 859.682 27 314.919 28 857.014 29 774.958 47 409.82 48 699.25e 48 701.60 48 745.40e
3
0 1 2 2 1 5 6 1 4 0 4 2 2
4f14 6s6p 4f14 6s6p 4f14 6s6p 4f13 5d6s2 4f14 6s6p 4f13 5d6s2 4f13 5d6s2 4f13 5d6s2 4f13 5d6s2 4f14 6s10p 4f14 6s9f 4f14 6s9ff 4f14 6s12p
Xy 65b Xy 65b Xy 65b Xq 76b Xy 32b Xq 80b Xq 83b Xq 57c Xq 80b Xy 65c Xy 65c Xy 65c Xy 65c
P P 3 P Ž7r2,3r2. 1 P Ž7r2,3r2. Ž7r2,5r2. Ž7r2,5r2. Ž7r2,5r2. 3 P,Ž1r2,1r2.d 3 F 3 f F 3 P 3
The values of the energy levels and their designations, J values and configurations are taken from Meggers and Tech w3x. DT values taken from Ahmad et al. w8x. c New DT values from the present study. d Designation for this level as given in Martin et al. w16x. e These levels are from Wyart and Camus w7x. f The level at 48701 cmy1 was unassigned in Meggers and Tech w3x and Martin et al. w16x, but assigned to 4f 14 6s9f in Wyart and Camus w7x which is confirmed presently. a
b
their assignment to 4f 13 5d6s6p configuration. For the level at 46 236 cmy1 Ž J s 3. of 4f 13 6s 2 6p, we have DTs ŽXq 76. mK which confirms the assignment. The term and assignment of the level at 47 420 cmy1 Ž J s 2. is given as 1 D Ž?. and 4f 14 6s9d Ž?. in Martin et al. w16x and present value of DTs ŽXy 76. mK confirms this assignment as indicated in Wyart and Camus w7x also. The level at 47 646 cmy1 has been assigned to 4f 13 5d6s6p in Maggers and Tech w3x but not in Martin et al. w16x and now the assignment has been revised to 4f 14 6s9d w7x, which is confirmed by our DT value of ŽXy 65. mK. The level at 47 646 cmy1 Ž J s 3. was assigned to 4f 13 5d6s6p configuration w16x but, our DT value of ŽXy 65. mK does not support this assignment, rather it supports the revised assignment of this level to 4f 14 6s9d w7x. DTs ŽX y 65. mK for the level at 48 364.89 cmy1 Ž J s 3. confirms its assignment to 4f 14 6s10d w7x. The unassigned level at 58 911 cmy1 Ž J s 5. has DTs ŽXq 5. mK which suggests 4f 13 5d6s6p configuration for this level. 3.2. DT-Values of the odd parity energy le¨ els of Yb I DT Ž 172 Yb] 176 Yb. for five odd parity levels
have been evaluated for the first time. The level at 28 857 cmy1 Ž J s 1., belonging to 4f 13 5d6s 2 configuration has DT value of ŽXq 57. mK. The DT value is low compared to other levels of 4f 13 5d6s 2 configuration having DT value around ŽXq 80. mK w8x. This level has been shown to have 48% Žf 7r2, d 5r2. and 22% Žf 5r2, d 3r2. by Nir w4x whereas Wyart and Camus w7x have assigned the leading component 3 P with 56% purity. The DT value of ŽXy 65. mK for both the levels at 47 409 cmy1 Ž J s 0. and 48 745 cmy1 Ž J s 2. confirm their assignments to f 14 sp configuration. For the level at 48 699 cmy1 Ž J s 4. of 4f 14 6s9f configuration, we have obtained DTs ŽX y 65. mK which confirms its assignment. The level at 48 701 cmy1 Ž J s 2. reported in Meggers and Tech w3x has been assigned to 4f 14 6s9f w7x and our value of DTs ŽXy 65. mK confirms this configuration assignment.
4. Conclusion Isotope shifts, involving isotopes 172 Yb and Yb, have been measured in few strong lines of Yb I in UV region. Term isotope shifts Ž DT. of the odd- and even-parity energy levels of Yb I 176
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reported earlier have been mostly confirmed. New DT values of 11 even- and five odd-parity levels have been reported and configuration assignments of these levels are discussed. References w1x A.S. King, Astrophys. J. 74 Ž1931. 328. w2x W.F. Meggers, B.F. Scribner, J. Res. NBS 19 Ž1937. 651]664. w3x W.F. Meggers, J.L. Tech, J. Res. NBS 88 Ž1978. 13]70. w4x S. Nir, Thesis, Hebrew University, Jerusalem Ž1969. 99]213 w5x N. Spector, J. Opt. Soc. Am. 61 Ž1971. 1350]1354. w6x P. Camus, A. Debarre, C. Morillon, J. Phys. B 11 Ž1978. L395. w7x J.F. Wyart, P. Camus, Phys. Scr. 20 Ž1979. 43]59. w8x S.A. Ahmad, I.J. Machado, G.D. Saksena, Spectrochim.
Acta Part B 35 Ž1980. 215]224. w9x H.-O. Behrens, G.H. Guthorlien, J. Phys. C7 Ž1983. ¨ 149]168. w10x J. Maier, C.S. Kischkel, M. Baumann, Z. Phys. D21 Ž1991. 145]151. w11x C.S. Kischkel, M. Baumann, E. Kummel, J. Phys. B25 Ž1992. 4447]4454. w12x W.A. van Wijngaarden, J. Li, J. Opt. Soc. Am. 11B Ž1994. 2163]2166. w13x S.M. Afzal, S.G. Nakhate, S.A. Ahmad, Z. Phys. D37 Ž1996. 249]253. w14x G.E. Miller, J.S. Ross, J. Opt. Soc. Am. 66 Ž1976. 585]589. w15x A.F. Golovin, A.R. Striganov, Opt. Spect. 9 Ž1965. 467]469. w16x W.C. Martin, R. Zalubas, L. Hagan, Atomic Energy Levels; The Rare Earth Elements, NSRDS-NBS 60, National Bureau of Standards, Washington, 1978.