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Investigation of the HFS in the 4d5 5p z7P3,4 states of 95Mo and 97Mo by levelcrossing spectroscopy
Volume 50, number 6
OPTICS COMMUNICATIONS
15 July 1984
INVESTIGATION OF THE HFS IN THE 4d 5 5p z7P3,4 STATES OF 95Mo AND 97Mo BY LEVELCROSSING SPECTROSCOPY M. BAUMANN, H. LINDEL and B. LINDENBERGER Physikalisches Institut der Universita't,Morgenstelle, 7400 1Yibingen,Fed. Rep. Germany Received 27 March 1984
The hyperf'me structures of the zTp3 and zVP4 states of 9SMo and 97Mo have been investigated by levelcrossing spectroscopy. A fit of the experimental signal curves yields the magnetic and electric hfs coupling constants: 9SMo zTP3 IAI = 86.19(10) MHz, IBI = 5.2(30) MHz, A/B > 0; 9SMo zTP4 IAI = 64.05(30) MHz, IBI = 4.3(30) MHz, A/B < 0; 97Mo zTP3 IAI= 88.0(1) MHz, IBI = 60.0(20) MHz,A/B < 0; 97Mo zTp4 IAI = 65.4(3) MHz, IBI = 50.0(50) MHz,A/B > 0. For the ratio of the electric quadrupole moments we f'md 97Q/gSQ = -11.5(70).
The ratio of the electric quadrupole moments of the isotopes 97Mo (1 = 5/2) and 95Mo (1= 5/2) has been determined by various authors [ 1 - 8 ] with different methods and with partially inconsistent results. The most precise value 97Q/95Q = -11.50(3) could be extracted from ABMR measurements in the metastable 4d 4 5s 2 a5D states [8]. Our experiment was performed primarily in order to derive this ratio from the hyperfine interaction in the odd parity configuration 4d 5 5p, where no hfs measurements have been published so far. The experimental set-up was that of a conventional Am = 2 levelcrossing measurement (e.g. [9]). An atomic beam of the highly enriched (95%) molybdenum isotope under study was produced in a high current oven of coaxial construction. The oven could be run at temperatures up to the melting point of Mo (2890 K). The atoms were irradiated by the resonance lines 3, = 386.411 nm (4d 5 5s 7S3--4d5 5p 7P3) and )~ = 379.825 nm (4d 5 5s 7S3---4d5 5p 7P4) from an intense hollow cathode lamp filled with a natural isotopic mixture of Mo. The exciting unpolarized light was directed perpendicularly to the magnetic field, which was generated by Helmholz coils. The fluorescence radiation from the excited states zTP 3 or zTP4 was observed in the direction of the magnetic field through a linear analyzer. The spectral lines were selected by a monochromator and detected with an EMI 0 030-4018/84/$03.00 © Elsevier Science Publishers B.V. (North-Holland Physics Publishing Division)
9625QB photomultiplier. The LC signals were modulated for lock-in detection by rotating the analyser. With regard to the long measuring times (typically 100 hours for one LC-signal curve) a continuous signal averaging technique by means of a multichannel analyser had to be applied [10]. Care had to be taken to avoid radiation trapping or distortion of the LC signals by the magnetic stray fields of the oven. The theoretical lineshape of the LC signals was calculated according to the Breit formula [11,12]. I = ~,
m ,m /z,#'
(mle i • Dl/a)(/ale i • Dim')
× (m'le o • Dl#')Iu,(/a'le o • Dim)~ [V - i(E m - E m ,)], where e i and e o are the polarisation vectors of the incident and emitted light, respectively, D is the electric dipole operator, V = h/2nr, with r as the mean lifetime of the excited state. Era, E m , are the energies of the excited state Zeeman sublevels. The summation has to be done over all excited (m, m') and groundstate ~,/~') levels. The influence of the line prof'de of the exciting radiation can approximately be accounted for by introducing the intensity parameters 1u, which denote the relative intensity absorbed by the groundstate hfs sublevel ta'. I~, could roughly be estimated from the known isotopic shift [13] and the abundance ratios of the Mo isotopes assuming a Gauss353
Volume 50, number 6
OPTICS COMMUNICATIONS
?.SO
15.01]
22. SO
B/mT
15 July 1984
profile for each isotope line. Besides the limited signal to noise ratio achievable, the accuracy o f the experiment was limited b y the precision o f the g j factors from [14]. Therefore it was sufficient to use the conventional hfs operator [ 15] when calculating the energies in the denominator o f the Breit formula without regarding second order corrections. As an example the hfs Zeeman effect o f the z7P3 state is shown in fig. 1 for 97Mo. The Am = 2 LC signals are strongly overlapping, so that a full resolution o f the LC peaks is n o t poss~le. Fig. 2 presents the measured signals for z7P3 o f 97Mo. The experimental signal curves were fitted b y calculating signals with the hfs coupling constants A and B as parameters. The values for r and g j were taken from the literature [10,14]. Table 1 presents the results for the magnetic hfs splitting constants A and the electric quadrupole coupling constants B. The ratio o f the quadrupole m o m e n t s 97Q/95Q = - 1 1 . 5 ( 7 0 ) is in agreement with the value recently obtained b y ABMR experiments [8].
F=I/2
/---V-3.7 GHz 4dSssa?S3
Fig. 1. Zeeman effect of the hfs in the 4d s 5p zTP3 state of 97Mo.The calculation was done withA = 88.0(1) MHz and B = -60.0(20) MHz. Am = 2 level crossings are marked by circles.
I F=11/2
&
23 [_ .,J
L o:
I
2.00
i
I
9.00
1{5.00
B/mT magnetic
v~,v~r,"--,'vw "-,,~-~-~vT'v,~',~wv'-F"
' r,,'~
field
Fig. 2. Measured and calculated Am = 2 LC curves for 97Moz7P3 with single LC signal components. The incident light is assumed to have a Gauss-profile corresponding to T = 1300 K. The difference between measurement and calculation is shown at the bottom. 354
Volume 50, number 6
OPTICS COMMUNICATIONS
15 July 1984
Table 1 Experimental values of the hfs coupling constants in the 4d s 5p, z 7 P3 and z 7 P4 states of 9SMo and 97Mo 95Mo zVP3 z7p4 97Mo zTP3 zTp4
1,41 = 86.19(10) 1,41 = 64.05(30) I,Zll= 88.0(1) ' 1,41 = 65.4(3)
MHz, MHz, MHz, MHz,
References [1] J. Kaufmarm, Z. Physik. 182 (1964) 217. [2] A. Narath and D.W. Alderman, Phys. Rev. 143 (1966) 328. [3] J.M. Pendlebury and D.B. Ring, J. Physics B5 (1972) 386. [4] S. Bfittgenbach, M. Herschel, G. Meisel, E. Schr6dl, W. Witte and W.J. Childs, Z. Physik 266 (1974) 271. [5] R.L. Void and R.R. Void, J. Mag. Res. 19 (1975) 365. [6] J. Kaufmann, J. Kronenbitter and A. Schwenk, Z. Physik A274 (1975) 87. [7] D.J. Blumer, C.P. Cheng and Th.L. Brown, Chem. Phys. Lett. 51 (1977)473.
IB[ = 5.2(30) tBI = 4.3(30) IBI = 60.0(20) IBI -- 50.0(50)
MHz, MHz, MHz, MHz,
A/B A/B A/B A/B
> O, < O, < O, > O.
[8] M. Dubke, W. Jitschin, G. Meisel and W.J. Childs, Phys. Lett. 65A (1978) 109. [9] M. Baumann, Z. Naturforsch. 24a (1969) 1049. [10] M. Baumann, H. Liening and H. Lindel, Phys. Letters 68A (1978) 319. [11] G. Breit, Rev. Mod. Phys. 5 (1933) 91. [12] P.A. Franken, Phys. Rev. 121 (1961) 508. [13] P. Aufmuth, H.P. Clieves, K. Heilig, A. Steudel, D. Wendlandt and J. Bauche, Z. Physik A285 (1978) 357. [14] C.E. Moore, Atomic energy levels, Vol. III, NBS Circular 467 (Washington, 1958). [15] N.F. Ramsey, Molecular beams (Oxford U.P. London, 1955) p. 272.
355
OPTICS COMMUNICATIONS
15 July 1984
INVESTIGATION OF THE HFS IN THE 4d 5 5p z7P3,4 STATES OF 95Mo AND 97Mo BY LEVELCROSSING SPECTROSCOPY M. BAUMANN, H. LINDEL and B. LINDENBERGER Physikalisches Institut der Universita't,Morgenstelle, 7400 1Yibingen,Fed. Rep. Germany Received 27 March 1984
The hyperf'me structures of the zTp3 and zVP4 states of 9SMo and 97Mo have been investigated by levelcrossing spectroscopy. A fit of the experimental signal curves yields the magnetic and electric hfs coupling constants: 9SMo zTP3 IAI = 86.19(10) MHz, IBI = 5.2(30) MHz, A/B > 0; 9SMo zTP4 IAI = 64.05(30) MHz, IBI = 4.3(30) MHz, A/B < 0; 97Mo zTP3 IAI= 88.0(1) MHz, IBI = 60.0(20) MHz,A/B < 0; 97Mo zTp4 IAI = 65.4(3) MHz, IBI = 50.0(50) MHz,A/B > 0. For the ratio of the electric quadrupole moments we f'md 97Q/gSQ = -11.5(70).
The ratio of the electric quadrupole moments of the isotopes 97Mo (1 = 5/2) and 95Mo (1= 5/2) has been determined by various authors [ 1 - 8 ] with different methods and with partially inconsistent results. The most precise value 97Q/95Q = -11.50(3) could be extracted from ABMR measurements in the metastable 4d 4 5s 2 a5D states [8]. Our experiment was performed primarily in order to derive this ratio from the hyperfine interaction in the odd parity configuration 4d 5 5p, where no hfs measurements have been published so far. The experimental set-up was that of a conventional Am = 2 levelcrossing measurement (e.g. [9]). An atomic beam of the highly enriched (95%) molybdenum isotope under study was produced in a high current oven of coaxial construction. The oven could be run at temperatures up to the melting point of Mo (2890 K). The atoms were irradiated by the resonance lines 3, = 386.411 nm (4d 5 5s 7S3--4d5 5p 7P3) and )~ = 379.825 nm (4d 5 5s 7S3---4d5 5p 7P4) from an intense hollow cathode lamp filled with a natural isotopic mixture of Mo. The exciting unpolarized light was directed perpendicularly to the magnetic field, which was generated by Helmholz coils. The fluorescence radiation from the excited states zTP 3 or zTP4 was observed in the direction of the magnetic field through a linear analyzer. The spectral lines were selected by a monochromator and detected with an EMI 0 030-4018/84/$03.00 © Elsevier Science Publishers B.V. (North-Holland Physics Publishing Division)
9625QB photomultiplier. The LC signals were modulated for lock-in detection by rotating the analyser. With regard to the long measuring times (typically 100 hours for one LC-signal curve) a continuous signal averaging technique by means of a multichannel analyser had to be applied [10]. Care had to be taken to avoid radiation trapping or distortion of the LC signals by the magnetic stray fields of the oven. The theoretical lineshape of the LC signals was calculated according to the Breit formula [11,12]. I = ~,
m ,m /z,#'
(mle i • Dl/a)(/ale i • Dim')
× (m'le o • Dl#')Iu,(/a'le o • Dim)~ [V - i(E m - E m ,)], where e i and e o are the polarisation vectors of the incident and emitted light, respectively, D is the electric dipole operator, V = h/2nr, with r as the mean lifetime of the excited state. Era, E m , are the energies of the excited state Zeeman sublevels. The summation has to be done over all excited (m, m') and groundstate ~,/~') levels. The influence of the line prof'de of the exciting radiation can approximately be accounted for by introducing the intensity parameters 1u, which denote the relative intensity absorbed by the groundstate hfs sublevel ta'. I~, could roughly be estimated from the known isotopic shift [13] and the abundance ratios of the Mo isotopes assuming a Gauss353
Volume 50, number 6
OPTICS COMMUNICATIONS
?.SO
15.01]
22. SO
B/mT
15 July 1984
profile for each isotope line. Besides the limited signal to noise ratio achievable, the accuracy o f the experiment was limited b y the precision o f the g j factors from [14]. Therefore it was sufficient to use the conventional hfs operator [ 15] when calculating the energies in the denominator o f the Breit formula without regarding second order corrections. As an example the hfs Zeeman effect o f the z7P3 state is shown in fig. 1 for 97Mo. The Am = 2 LC signals are strongly overlapping, so that a full resolution o f the LC peaks is n o t poss~le. Fig. 2 presents the measured signals for z7P3 o f 97Mo. The experimental signal curves were fitted b y calculating signals with the hfs coupling constants A and B as parameters. The values for r and g j were taken from the literature [10,14]. Table 1 presents the results for the magnetic hfs splitting constants A and the electric quadrupole coupling constants B. The ratio o f the quadrupole m o m e n t s 97Q/95Q = - 1 1 . 5 ( 7 0 ) is in agreement with the value recently obtained b y ABMR experiments [8].
F=I/2
/---V-3.7 GHz 4dSssa?S3
Fig. 1. Zeeman effect of the hfs in the 4d s 5p zTP3 state of 97Mo.The calculation was done withA = 88.0(1) MHz and B = -60.0(20) MHz. Am = 2 level crossings are marked by circles.
I F=11/2
&
23 [_ .,J
L o:
I
2.00
i
I
9.00
1{5.00
B/mT magnetic
v~,v~r,"--,'vw "-,,~-~-~vT'v,~',~wv'-F"
' r,,'~
field
Fig. 2. Measured and calculated Am = 2 LC curves for 97Moz7P3 with single LC signal components. The incident light is assumed to have a Gauss-profile corresponding to T = 1300 K. The difference between measurement and calculation is shown at the bottom. 354
Volume 50, number 6
OPTICS COMMUNICATIONS
15 July 1984
Table 1 Experimental values of the hfs coupling constants in the 4d s 5p, z 7 P3 and z 7 P4 states of 9SMo and 97Mo 95Mo zVP3 z7p4 97Mo zTP3 zTp4
1,41 = 86.19(10) 1,41 = 64.05(30) I,Zll= 88.0(1) ' 1,41 = 65.4(3)
MHz, MHz, MHz, MHz,
References [1] J. Kaufmarm, Z. Physik. 182 (1964) 217. [2] A. Narath and D.W. Alderman, Phys. Rev. 143 (1966) 328. [3] J.M. Pendlebury and D.B. Ring, J. Physics B5 (1972) 386. [4] S. Bfittgenbach, M. Herschel, G. Meisel, E. Schr6dl, W. Witte and W.J. Childs, Z. Physik 266 (1974) 271. [5] R.L. Void and R.R. Void, J. Mag. Res. 19 (1975) 365. [6] J. Kaufmann, J. Kronenbitter and A. Schwenk, Z. Physik A274 (1975) 87. [7] D.J. Blumer, C.P. Cheng and Th.L. Brown, Chem. Phys. Lett. 51 (1977)473.
IB[ = 5.2(30) tBI = 4.3(30) IBI = 60.0(20) IBI -- 50.0(50)
MHz, MHz, MHz, MHz,
A/B A/B A/B A/B
> O, < O, < O, > O.
[8] M. Dubke, W. Jitschin, G. Meisel and W.J. Childs, Phys. Lett. 65A (1978) 109. [9] M. Baumann, Z. Naturforsch. 24a (1969) 1049. [10] M. Baumann, H. Liening and H. Lindel, Phys. Letters 68A (1978) 319. [11] G. Breit, Rev. Mod. Phys. 5 (1933) 91. [12] P.A. Franken, Phys. Rev. 121 (1961) 508. [13] P. Aufmuth, H.P. Clieves, K. Heilig, A. Steudel, D. Wendlandt and J. Bauche, Z. Physik A285 (1978) 357. [14] C.E. Moore, Atomic energy levels, Vol. III, NBS Circular 467 (Washington, 1958). [15] N.F. Ramsey, Molecular beams (Oxford U.P. London, 1955) p. 272.
355