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Chemical effect on L X-ray fluorescence cross-sections of Hg, Pb and Bi compounds
SPECTROCHIMICA ACTA PART B
ELSEVIER
Spectrochimica Acta Part B 52 (1997) 1167-1171
Chemical effect on L X-ray fluorescence cross-sections of Hg, Pb and B i compounds E. Btiytikkasap Atat~rk University, Faculty of Education, Department of Physics Education, 25240 Erzurum, Turkey
Received 15 October 1996; accepted 10 January 1997
Abstract Chemical effect on the photon induced L X-ray fluorescence cross-sections (aL~, OLBand aLv) for Hg, Pb and Bi compounds were investigated. The samples were excited by gamma rays with energy 59.5 keV from 24~Am radioisotope source. L X-rays emitted by samples were counted by a Si(Li) detector with resolution 160 eV at 5.9 keV. We observed chemical effect on the photon induced L X-ray fluorescence cross-sections (aL~, OL~ and OLv) for Hg, Pb and Bi compounds. Our values were compared with calculated theoretical values. © 1997 Elsevier Science B.V. Keywords: X-ray fluorescence cross-sections; Chemical effect
I. Introduction Information regarding experimental K and L X-ray fluorescence cross-sections and relative intensity ratios for different elements is important because of its wide use in the fields of atomic, molecular and radiation physics and non-destructive analysis of materials using energy dispersive XRF techniques. Several studies [1-8] concerned with L X-ray fluorescence cross-sections were made. Some researchers [9] calculated theoretical L X-ray fluorescence crosssections. Although effects of excitation mode and excitation energy on L X-ray fluorescence crosssections were studied, there is no study interested with chemical effect on L X-ray fluorescence crosssections. Li X-ray emission lines are caused by transition Lc~ = (L 3 ,--- Ms,M4); Lfl = ( L I ~-- M2,M3; L3 ~-N5,O4,O5; L2 ~-- M4); L3' = (Ll '--- N2,N3,O3; L2 N4,O4) and Lt = (L3 *---MI). It is well known that X-ray spectra depend on the chemical surroundings of the atom. Especially, K
X-ray intensity ratios and K X-ray fluorescence cross-sections of 3d elements strongly depend on chemical state. We investigated chemical effect [10-12], alloying effect ]13], thickness effect [14] on the K X-ray intensity ratios and alloying effect [15] on K X-ray fluorescence cross-sections. In addition to these, we measured K X-ray intensity ratios following radioactive decay and photoionisation [16]. Limited work [17,18] has been done concerned with chemical effect on L X-ray intensity ratios. We investigated chemical effect on L X-ray intensity ratios [ 19]. In the present study, chemical effect on the photon induced L X-ray fluorescence cross-sections (aL~, ale and aLv) for Hg, Pb and Bi compounds were investigated.
2. Experimental Experimental measurements were carried out on the L characteristic radiations stimulated by
0584-8547/97/$17.00 © 1997 Elsevier Science B.V. All rights reserved. PH S05 84-8547(97)00008-6
1168
E. Bi~yiikkasap/SpectrochimicaActa Part B 52 (1997) 1167-1171
59.5 keV gamma photons of a 100 mCi 241Am source in HgI2, HgCI2, Hg2(NO3)2.2H20, Hg(NO3)2, HgSO4, Pb, PbO2, Pb(CH3COO)z.3H20, Pb(NO3)2, PbCO3, Pb304, Bi203, Bi(NO3)y5H20, Bi2(CO3)3, BiC13, BiOCI. Powder samples were sieved for 400 mesh and prepared by supporting on a Mylar film at 2-10 × 10-3g cm -2 thickness. The Si(Li) detector which had a resolution 160 eV at 5.9 keV and ND66B pulse height analyser were used to count Lot, L/3 and L3' photons emitted from samples. The experimental setup and L X-ray spectra of Hg2(NO3)2.2HzO and Hg(NO3)2 are given in Figs 1 and 2 respectively. As shown in Fig. 1, the lead shield avoided the direct exposure of the detector to radiation from the source. Iron lining on its inner side was used to avoid the Pb L X-rays. The aluminium lining was used to collimate the K X-rays from iron. The Lot, L~ and L7 X-ray fluorescence crosssections have been calculated using the relation [2-4]
the energy of Li X-rays. L a is a little bit stronger than Lj3 according to multiplet theory without considering the Coster-Kronig transitions. L~ is made a little stronger than L a by the Coster-Kronig transitions. Since the self-absorption effect and detector efficiency effect are different for different energy, it seems that Lo~ is slightly stronger than L~ in Fig. 2. The corrections for these effects were made on measured values in Eq. (1). loGe values in the present experimental setup were determined in a separate experiment. Targets of pure elements, having areas of physical cross-section similar to those used in the main experiment, with atomic number 22 -- Z - 40, emitting fluorescent X-rays in the energy range 4.5-18 keV were irradiated in the same geometry and fluorescent X-rays were counted, loGe values for the present setup were determined by the following relationship [2-4] NKi loGe = - OKi[3imj
(1)
NLi OLi -- loGt3il~im i
where NKi is the number of K~ or K a X-rays recorded under the K~ or Kot peaks; OKi is the aK~ or aK,~fluorescence cross-section. The self absorption correction has been calculated by using the following expression [1] obtained by assuming the incidence angle of the fluorescent X rays subtended at the detector to be approximately 90 ° .
where NLi is the intensity observed for the Li X-ray line of the element, I0 the intensity of exciting radiation, G the geometry factor, mi the mass of the element in sample (g cm-2), ~ the target self absorption correction factor both the incident and emitted radiation, and ei the detection efficiency of the detector at
~
(2)
Sampel ~
Fig. 1. Experimentalarrangement.
RadioactiveSource
E. Biiyiikkasap/Spectrochimica Acta Part B 52 (1997) 1167-1171 I
8000
!
i
I
|
calculated as 48 ° . In addition to this, we have also checked the angle, from the shift in energy of the incoherent scattered peak from the coherent peak using Compton scattering formula.
Hg2(NO3)2 x 2 H 2 0
7000 6000 L~
LX~
50O0
3. Results and discussion
~oO0
3000 2000 I T
I000
Ll
~ .
• TI..•;'
72
95
•
117
139
1fi3
lf16
?09
731
Ch,-~n n e I 8030
t
I
i
I
I
i
i
Hg(NO3)2
700C 60t~
The measured values of the Lo~, L3 and L~ crosssections in HgI2, HgCI2, Hg2(NO3)z.2H20, Hg(NO3)2, HgSO4, Pb, PbO2, Pb(CH3COO)2.3H20, Pb(NO3)2, PbCO3, Pb304, Bi203, Bi(NO3)y5H20, Bi2(CO3)3, BiCI3, BiOC1 are listed in Table 1. The values of La, L3 and L7 cross-sections are calculated from theoretical values of L subsheli photoionisation cross-sections [22] and radiative decay rates [23], semi-empirically fitted values of fluorescence yields [24] and Coster-Kronig transition probabilities [24] using following relations O-L~ = (Olf13 + alf12f23 + O'2f23 + 03)co3F3c ~
aLt3 = 01 col Fj~ + (a 2 + a2 fl2)co2F2~
L(~
4ooo,
5
1169
L~
+ (olf13 + olfl 2f23 + 02f23 + o3)w3F3B
3000
OL.y = al col Fi-r + (a2 + a2 fl 2)co2F2") '
0
2000
LjL
'I,000
.
.~
b6
91
•
.
114
•
-
Lt
.
•
138
161
1["15
:'08
731
Chann e I
Fig. 2. L X-ray spectra of Hg2(NO3)z.2H.~O and Hg(NO3)2. ~emt = I - e x p [ ( - 1)(#i,c/cos ~+/Xemt)t ] (/Zinc/cos q~ +/Zemt)t
(3)
where IXi°c (cm2g -I) and l~emt (cm2g -1) are the mass absorption coefficients [20] at the incident photon energy and fluorescent X-ray energy of the sample respectively; t (g cm -2) is the measured thickness of the sample• 4) has been calculated by using the following expression [21 ] V
cos ~b-- [v 2 +0.25(R0 + RI)2] 1/2
(4)
where v is the distance from the source to the sample, and R0 and R] the internal and external diameters of radioisotope source respectively. 4) has been
where ol, 02 and a3 are L subshell photoionisation cross-sections of element at 59.5 keV; co], o:2 and 0:3 are L subshell fluorescence yields; f12, f23 and fl3 are intra-L shell Coster-Kronig transition probabilities, Fs are fractional radiative decay rates, and F3~ is the fraction of Lm subshell X-rays which contributes to the Lo~ peak of the X-ray spectrum of an element. All other Fs are similarly defined. The errors in the present measurements are approximately 7 - 8 % and are due to counting statistics, background determination, self-absorption correction and loGa determination. In some Hg and Bi compounds, iodine exerts an enhancement effect on L, M . . . . . shells; sulphur and chlorine exert an enhancement effect on M, N . . . . . shells (and also cause a Coster-Kronig transition). This effect changes cross-section values by approximately 5 6% [25-27]. This effect is not present in the other compounds. It is well known that orbital energy levels of L, M, N, O and P shells get closer to each other with increasing quantum number n. Outer energy levels were
1170
E. Biiyiikkasap/Spectrochimica Acta Part B 52 (1997) 1167-1171
Table I L X-ray cross-sections (barn atom ~) Compound
Hg HgI2 HgCI2 Hg2(NO3)2.2H~O Hg(NO3)2 HgSO4 Pb PbO2 Pb(CH3COO)2.3H20 Pb(NO3)2 PbCOs Pb30~ Bi Bi203 Bi(NOs)3.5H20 Bi2(CO3)~ BiCI 3 BiOCI
ac~
O'Lfl
OL3~
Present
Calculated
Present
Calculated
Present
Calculated
147 134 109 141 104 154 169 186 144 176 165 156 237 237 117 198
156
176 157 129 170 122 191 210 308 176 210 197 205 303 304 153 245
158
47 37 29 39 29 46 55 65 46 51 49 41 69 85 41 62
28.8
± 12 ± 11 -+ 9 -+ 11 ± 8 ± 12 ± 14 ± 15 -+ 12 ± 14 ± 13
192
205 ÷ 12 -+ 19 ± 21 ± 9 ± 16
made sensitive to the chemical environment by this effect. Thus, outer energy levels are strongly affected by ligands with respect to crystal field theory. These effects play an important role in the La, LB and L'y Xray transitions. Since Hg has an unfilled 5s shell, and Pb and Bi have an unfilled 6p shell, these elements are sensitive to these effects. Because Coster-Kronig transitions include the valence electrons, the chemical effect on the fluorescence yield is due to the chemical effects on the f12, f23 and f13 Coster-Kronig transitions. Different molecules have different bond energies and these energies give us information about bond distances between ligands and central atoms. Different bond distances and bond energies cause different interaction between ligands and central atoms. Thus; Lo~, Lt3 and L~/ fluorescence cross-sections change by changing bond energies. To reach a more definitive conclusion about chemical effects on the L X-ray fluorescence cross-section, we plan to extend these measurements for various element and various compound. References [I] K. Shatendra, K.L. AIlawadhi, B.S. Sood, Phys. Rev. A31 (5) (1985) 2918.
± 10 ± 13 ± 10 ± 14 ± 9 ± 15 ± 17 ± 25 -+ 14 ± 17 ± 16
216
217 ÷ -+ ± -+ -+
16 24 24 12 20
÷ 4 ± 3 ± 2 -+ 3 -- 2 ÷ 4 _+ 4 ± 5 ± 3 ± 4 _+ 3
40.9
41.4 _+ 3 ~ 6 ± 7 ± 3 ± 5
[2] M.L. Garg, S. Kumar, D. Mehta, H.R. Verma, P.C. Mangal, P.N. Trehan, J. Phys. B: At. Mol. Phys. 18 (1985) 4529. [3] C. Bhan, S.N. Chaturvedi, N. Nath, X-Ray Spectrom. 15 (1986) 217. [4] S. Singh, D. Mehta, M.L. Garg, S. Kumar, N. Singh, P.C. Mangal, P.N. Trehan, J. Phys. B: At. Mol. Phys. 20 (1987) 3325. [5] S. Singh, B. Chand, D. Mehta, S. Kumar, M.L. Garg, N. Singh, P.C. Mangal, P.N. Trehan, J. Phys. B: At. Mol. Phys. 22 (1989) 1163. [6] K.S. Mann, N. Singh, R. Mittal, B.S. Sood, J. Phys. B: At. Mol. Phys. 23 (1990) 3531. [7] D.V. Rao, R. Cesareo, G.E. Gigante, X-Ray Spectrom. 22 (1993) 401. [8] M.L. Garg, R.R. Garg, K.G. Malmqvist, J. Phys. B: At. Mol. Phys. 20 (1987) 3705. [9] M.O. Krause, Jr. C.W. Nestor, C.J. Sparks, E. Ricci, Oak Ridge National Laboratory Rep. ORNL 5399, 1978. [10] A. Ktiqiik6nder, Y. Sahin, E. Btiytikkasap, J. Radioanal. Nucl. Chem. Article, 170 (I) (1993) 125. [11] A. KaqUk6nder, Y. Sahin, E. Btiytikkasap, A.I. Kopya, J. Phys. B26 (1993) 101. [12] A. KiiqiiktJnder, Y. Sahin, E. Btiytikkasap, IL Nuovo Cimento 15D (10) (1993) 1295. [ 13] O. S6~tit, E. Biiyiikkasap, A. Kti~i.ik6nder, M. Ertu~rul and O. ~im~,ek, Appl. Spect. Rev., 30 (3) (1995) 175. [14] E. B/iy0.kkasap, Appl. Spect. Rev., in press. [15] E. Btiy~kkasap, unpublished. [16] E. Biiytikkasap, A. Ktiqiak6nder, Y. Sahin, H. Erdo~an, J. Radioanal. Nucl. Chem. Lett., 186 (6) (1994) 471. [17] J. Kawai, K. Nakajima, K. Maeda, Y. Goshi, Adv. X-Ray Anal. 35 (1992) 1107.
E. Biiyiikkasap/Spectrochimica
[18] A.V. Tyunis, Y.P. Smirnov, A.E. Sovestnov, V.A. Shaburov, I.M. Band, M.B. Trzhaskovskaya, Phys. Solid State, 36 (9) (1994) 1489. [19] E. B0yiikkasap, O. S6~tit, A. Ktiqtik~nder, M. Ertu(grul, unpublished. [20] J.H. Hubbell, S.M. Seltzer, U.S. Department of Commerce, Technology Administration, National Institute of Standards and Physics Laboratory, NISTIR 5692, 1995. [21] A. Zararsiz, E. Aygiin, J. Radioanal. Nucl. Chem., Articles 129 (1989) 367.
Acta Part B 52 (1997) 1167-1171
1171
[22] J.H. Scofield, Lawrence Livermore Laboratory, Rep. UCRL 51326, 1973. [23] J.H. Scofield, Phys. Rev. A179 (1969) 9. [24] M.O. Krause, J. Phys. Chem. Data, 8 (1979) 307. [25] E.B. Benin, Principles and Practice of X-Ray Spectrometric Analysis, Plenum, New York, 1975. [26] R. Tertian, F. Claisse, Principles of Quantitative X-Ray Fluorescence Analysis, Heyden, London, 1982. [27] R. Jenkins, An Introduction to X-Ray Spectrometry, Wiley, New York, 1986.
ELSEVIER
Spectrochimica Acta Part B 52 (1997) 1167-1171
Chemical effect on L X-ray fluorescence cross-sections of Hg, Pb and B i compounds E. Btiytikkasap Atat~rk University, Faculty of Education, Department of Physics Education, 25240 Erzurum, Turkey
Received 15 October 1996; accepted 10 January 1997
Abstract Chemical effect on the photon induced L X-ray fluorescence cross-sections (aL~, OLBand aLv) for Hg, Pb and Bi compounds were investigated. The samples were excited by gamma rays with energy 59.5 keV from 24~Am radioisotope source. L X-rays emitted by samples were counted by a Si(Li) detector with resolution 160 eV at 5.9 keV. We observed chemical effect on the photon induced L X-ray fluorescence cross-sections (aL~, OL~ and OLv) for Hg, Pb and Bi compounds. Our values were compared with calculated theoretical values. © 1997 Elsevier Science B.V. Keywords: X-ray fluorescence cross-sections; Chemical effect
I. Introduction Information regarding experimental K and L X-ray fluorescence cross-sections and relative intensity ratios for different elements is important because of its wide use in the fields of atomic, molecular and radiation physics and non-destructive analysis of materials using energy dispersive XRF techniques. Several studies [1-8] concerned with L X-ray fluorescence cross-sections were made. Some researchers [9] calculated theoretical L X-ray fluorescence crosssections. Although effects of excitation mode and excitation energy on L X-ray fluorescence crosssections were studied, there is no study interested with chemical effect on L X-ray fluorescence crosssections. Li X-ray emission lines are caused by transition Lc~ = (L 3 ,--- Ms,M4); Lfl = ( L I ~-- M2,M3; L3 ~-N5,O4,O5; L2 ~-- M4); L3' = (Ll '--- N2,N3,O3; L2 N4,O4) and Lt = (L3 *---MI). It is well known that X-ray spectra depend on the chemical surroundings of the atom. Especially, K
X-ray intensity ratios and K X-ray fluorescence cross-sections of 3d elements strongly depend on chemical state. We investigated chemical effect [10-12], alloying effect ]13], thickness effect [14] on the K X-ray intensity ratios and alloying effect [15] on K X-ray fluorescence cross-sections. In addition to these, we measured K X-ray intensity ratios following radioactive decay and photoionisation [16]. Limited work [17,18] has been done concerned with chemical effect on L X-ray intensity ratios. We investigated chemical effect on L X-ray intensity ratios [ 19]. In the present study, chemical effect on the photon induced L X-ray fluorescence cross-sections (aL~, ale and aLv) for Hg, Pb and Bi compounds were investigated.
2. Experimental Experimental measurements were carried out on the L characteristic radiations stimulated by
0584-8547/97/$17.00 © 1997 Elsevier Science B.V. All rights reserved. PH S05 84-8547(97)00008-6
1168
E. Bi~yiikkasap/SpectrochimicaActa Part B 52 (1997) 1167-1171
59.5 keV gamma photons of a 100 mCi 241Am source in HgI2, HgCI2, Hg2(NO3)2.2H20, Hg(NO3)2, HgSO4, Pb, PbO2, Pb(CH3COO)z.3H20, Pb(NO3)2, PbCO3, Pb304, Bi203, Bi(NO3)y5H20, Bi2(CO3)3, BiC13, BiOCI. Powder samples were sieved for 400 mesh and prepared by supporting on a Mylar film at 2-10 × 10-3g cm -2 thickness. The Si(Li) detector which had a resolution 160 eV at 5.9 keV and ND66B pulse height analyser were used to count Lot, L/3 and L3' photons emitted from samples. The experimental setup and L X-ray spectra of Hg2(NO3)2.2HzO and Hg(NO3)2 are given in Figs 1 and 2 respectively. As shown in Fig. 1, the lead shield avoided the direct exposure of the detector to radiation from the source. Iron lining on its inner side was used to avoid the Pb L X-rays. The aluminium lining was used to collimate the K X-rays from iron. The Lot, L~ and L7 X-ray fluorescence crosssections have been calculated using the relation [2-4]
the energy of Li X-rays. L a is a little bit stronger than Lj3 according to multiplet theory without considering the Coster-Kronig transitions. L~ is made a little stronger than L a by the Coster-Kronig transitions. Since the self-absorption effect and detector efficiency effect are different for different energy, it seems that Lo~ is slightly stronger than L~ in Fig. 2. The corrections for these effects were made on measured values in Eq. (1). loGe values in the present experimental setup were determined in a separate experiment. Targets of pure elements, having areas of physical cross-section similar to those used in the main experiment, with atomic number 22 -- Z - 40, emitting fluorescent X-rays in the energy range 4.5-18 keV were irradiated in the same geometry and fluorescent X-rays were counted, loGe values for the present setup were determined by the following relationship [2-4] NKi loGe = - OKi[3imj
(1)
NLi OLi -- loGt3il~im i
where NKi is the number of K~ or K a X-rays recorded under the K~ or Kot peaks; OKi is the aK~ or aK,~fluorescence cross-section. The self absorption correction has been calculated by using the following expression [1] obtained by assuming the incidence angle of the fluorescent X rays subtended at the detector to be approximately 90 ° .
where NLi is the intensity observed for the Li X-ray line of the element, I0 the intensity of exciting radiation, G the geometry factor, mi the mass of the element in sample (g cm-2), ~ the target self absorption correction factor both the incident and emitted radiation, and ei the detection efficiency of the detector at
~
(2)
Sampel ~
Fig. 1. Experimentalarrangement.
RadioactiveSource
E. Biiyiikkasap/Spectrochimica Acta Part B 52 (1997) 1167-1171 I
8000
!
i
I
|
calculated as 48 ° . In addition to this, we have also checked the angle, from the shift in energy of the incoherent scattered peak from the coherent peak using Compton scattering formula.
Hg2(NO3)2 x 2 H 2 0
7000 6000 L~
LX~
50O0
3. Results and discussion
~oO0
3000 2000 I T
I000
Ll
~ .
• TI..•;'
72
95
•
117
139
1fi3
lf16
?09
731
Ch,-~n n e I 8030
t
I
i
I
I
i
i
Hg(NO3)2
700C 60t~
The measured values of the Lo~, L3 and L~ crosssections in HgI2, HgCI2, Hg2(NO3)z.2H20, Hg(NO3)2, HgSO4, Pb, PbO2, Pb(CH3COO)2.3H20, Pb(NO3)2, PbCO3, Pb304, Bi203, Bi(NO3)y5H20, Bi2(CO3)3, BiCI3, BiOC1 are listed in Table 1. The values of La, L3 and L7 cross-sections are calculated from theoretical values of L subsheli photoionisation cross-sections [22] and radiative decay rates [23], semi-empirically fitted values of fluorescence yields [24] and Coster-Kronig transition probabilities [24] using following relations O-L~ = (Olf13 + alf12f23 + O'2f23 + 03)co3F3c ~
aLt3 = 01 col Fj~ + (a 2 + a2 fl2)co2F2~
L(~
4ooo,
5
1169
L~
+ (olf13 + olfl 2f23 + 02f23 + o3)w3F3B
3000
OL.y = al col Fi-r + (a2 + a2 fl 2)co2F2") '
0
2000
LjL
'I,000
.
.~
b6
91
•
.
114
•
-
Lt
.
•
138
161
1["15
:'08
731
Chann e I
Fig. 2. L X-ray spectra of Hg2(NO3)z.2H.~O and Hg(NO3)2. ~emt = I - e x p [ ( - 1)(#i,c/cos ~+/Xemt)t ] (/Zinc/cos q~ +/Zemt)t
(3)
where IXi°c (cm2g -I) and l~emt (cm2g -1) are the mass absorption coefficients [20] at the incident photon energy and fluorescent X-ray energy of the sample respectively; t (g cm -2) is the measured thickness of the sample• 4) has been calculated by using the following expression [21 ] V
cos ~b-- [v 2 +0.25(R0 + RI)2] 1/2
(4)
where v is the distance from the source to the sample, and R0 and R] the internal and external diameters of radioisotope source respectively. 4) has been
where ol, 02 and a3 are L subshell photoionisation cross-sections of element at 59.5 keV; co], o:2 and 0:3 are L subshell fluorescence yields; f12, f23 and fl3 are intra-L shell Coster-Kronig transition probabilities, Fs are fractional radiative decay rates, and F3~ is the fraction of Lm subshell X-rays which contributes to the Lo~ peak of the X-ray spectrum of an element. All other Fs are similarly defined. The errors in the present measurements are approximately 7 - 8 % and are due to counting statistics, background determination, self-absorption correction and loGa determination. In some Hg and Bi compounds, iodine exerts an enhancement effect on L, M . . . . . shells; sulphur and chlorine exert an enhancement effect on M, N . . . . . shells (and also cause a Coster-Kronig transition). This effect changes cross-section values by approximately 5 6% [25-27]. This effect is not present in the other compounds. It is well known that orbital energy levels of L, M, N, O and P shells get closer to each other with increasing quantum number n. Outer energy levels were
1170
E. Biiyiikkasap/Spectrochimica Acta Part B 52 (1997) 1167-1171
Table I L X-ray cross-sections (barn atom ~) Compound
Hg HgI2 HgCI2 Hg2(NO3)2.2H~O Hg(NO3)2 HgSO4 Pb PbO2 Pb(CH3COO)2.3H20 Pb(NO3)2 PbCOs Pb30~ Bi Bi203 Bi(NOs)3.5H20 Bi2(CO3)~ BiCI 3 BiOCI
ac~
O'Lfl
OL3~
Present
Calculated
Present
Calculated
Present
Calculated
147 134 109 141 104 154 169 186 144 176 165 156 237 237 117 198
156
176 157 129 170 122 191 210 308 176 210 197 205 303 304 153 245
158
47 37 29 39 29 46 55 65 46 51 49 41 69 85 41 62
28.8
± 12 ± 11 -+ 9 -+ 11 ± 8 ± 12 ± 14 ± 15 -+ 12 ± 14 ± 13
192
205 ÷ 12 -+ 19 ± 21 ± 9 ± 16
made sensitive to the chemical environment by this effect. Thus, outer energy levels are strongly affected by ligands with respect to crystal field theory. These effects play an important role in the La, LB and L'y Xray transitions. Since Hg has an unfilled 5s shell, and Pb and Bi have an unfilled 6p shell, these elements are sensitive to these effects. Because Coster-Kronig transitions include the valence electrons, the chemical effect on the fluorescence yield is due to the chemical effects on the f12, f23 and f13 Coster-Kronig transitions. Different molecules have different bond energies and these energies give us information about bond distances between ligands and central atoms. Different bond distances and bond energies cause different interaction between ligands and central atoms. Thus; Lo~, Lt3 and L~/ fluorescence cross-sections change by changing bond energies. To reach a more definitive conclusion about chemical effects on the L X-ray fluorescence cross-section, we plan to extend these measurements for various element and various compound. References [I] K. Shatendra, K.L. AIlawadhi, B.S. Sood, Phys. Rev. A31 (5) (1985) 2918.
± 10 ± 13 ± 10 ± 14 ± 9 ± 15 ± 17 ± 25 -+ 14 ± 17 ± 16
216
217 ÷ -+ ± -+ -+
16 24 24 12 20
÷ 4 ± 3 ± 2 -+ 3 -- 2 ÷ 4 _+ 4 ± 5 ± 3 ± 4 _+ 3
40.9
41.4 _+ 3 ~ 6 ± 7 ± 3 ± 5
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E. Biiyiikkasap/Spectrochimica
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1171
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