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Compton profiles of liquid and solid lithium metals
Volume 57A, number I
PHYSICS LETTERS
17 May 1976
COMPTON PROFILES OF LIQUID AND SOLID LITHIUM METALS K. SUZUKI, F. ITOH, T. HONDA and M. KUROHA The Reseai~chInstitute for Iron, Steel and Other Metals, Tohoku University, Sendai, Japan Received 12 March 1976
241
Compton profile measurements have been performed on liquid and solid lithium metal using 59.54 keV ~y-rayfrom Am source. A difference between Compton profiles in both states has been found.
Compton profiles of lithium metals in the liquid state as well as in the solid state have been measured using 59.54 keV -y-rays from a 45 mCi 24 1Am point source and a solid state detector Ge(Li). Lithium metal was contained in a cylindrical yessel with 16 mm inner diameter and 20 mm length made of iron. Both opening sides of the vessel were sealed with iron sheets of 0.005 mm thickness, through which incident ~-ray entered into the specimen. Scattered y-rays were emitted from the specimen with a scattering angle 165°. Measurements were first carried out in the liquid state at 2 20°Cand theii in the solid state at 25°C without changing the initial arrangement of the detector system and specimen. In each run, about 12000 counts per channel were accumulated at the position of the common peak. Background measurements were carried out with the same vessel before filling the specimen and subtracted from the total spectrum after proper normalization. Experimental data thus obtained were processed into a Compton profile J(q) following the procedure of Manninnen et al. [1] The generalized least squares method [2] was adopted as a deconvolution procedure. Fig. 1 shows Compton profiles J(q) observed for liquid and solid lithium. For small q-values a signifi-
1 8 16-
LITHIUM
1 4
.
:
10—
SOLID
.
~O8
~ O4~
o 2~— -
6
4
2
0 u )
2
1.
6
Fig. 1. Experimental Colnpton profilesf(q) for liquid and solid lithium metal. The dashed curve means the contribution of inner calculated in the impulse tion wingcore freeelectrons atom function by Clenienti 151. approxima0 ~
EXPERIMENT THEORY
.
cant difference can be should found between thepositron liquid and solid state. in This result be compared with that of experiments on angular in annihilation, which such a correlation significant difference has not been observed [3] On the other hand, the value of .1~~~(0) for solid lithium metal in this work lies below that reported by Wachtel et al. [4] which is per-
LIQUID .
1 2
0 05
..
..
—2
—
1
••••l•__
j
I 0
-
~ 1
2
.
,
haps due to the effect of multiple scattering, The difference between the Compton profiles J(q)
Fig. 2. Experimental and theoretical difference curves of Compton profiles, L~J(q)— ~liq (q) J 50~(q).See text. The error bars in the experimental difference curve mean the statistical error.
95
Volume 57A, number I
PHYSiCS LFTFLRS
of liquid and solid lithium metal is plotted in fig. 2. Fig. 2 can be thought to reflect a change of the deetronic structure of the conduction electrons in Iithium nietal upon melting, because the contribution of multiple scattering to Compton profiles is most likely the same in both states and will cancel. The solid line in fig. 2 denotes a theoretical diffetenee curve which is obtained by deconvoluting the theoretical function based upon the free electron model convoluted with the instrumental resolution function, using the same parameters as used to obtain experimental profiles. This theoretical curve is in good agreement with the experimental one, which suggests that the change of the electronic structure in lithium metal Upon melting can he qualitatively explained by the free
96
17 May 1976
electron model. Further experiments are in progress using thinner
samples to avoid the contribution of multiple scatter ing
References
Ill 121 131 141 151
S. Manninen, T. Paakkari and K. Kajantic, Phil. Mag 29 (1974) 167. P. Paatero, 5. Manninen and T. Paakkari, Phil. Mag. 30 AT. Stewart, Positron annihilation (Acadenm. Press, New York, 1967) p. 17. S. Wachtel, J. Fclsteiner, S. Kahane and R. Ophcr, Phys. Rev. B 12 (1975) 1285. I . Clcmenti, IBM J. Rcs. Develop. Suppl. 9 (1965) 2.
PHYSICS LETTERS
17 May 1976
COMPTON PROFILES OF LIQUID AND SOLID LITHIUM METALS K. SUZUKI, F. ITOH, T. HONDA and M. KUROHA The Reseai~chInstitute for Iron, Steel and Other Metals, Tohoku University, Sendai, Japan Received 12 March 1976
241
Compton profile measurements have been performed on liquid and solid lithium metal using 59.54 keV ~y-rayfrom Am source. A difference between Compton profiles in both states has been found.
Compton profiles of lithium metals in the liquid state as well as in the solid state have been measured using 59.54 keV -y-rays from a 45 mCi 24 1Am point source and a solid state detector Ge(Li). Lithium metal was contained in a cylindrical yessel with 16 mm inner diameter and 20 mm length made of iron. Both opening sides of the vessel were sealed with iron sheets of 0.005 mm thickness, through which incident ~-ray entered into the specimen. Scattered y-rays were emitted from the specimen with a scattering angle 165°. Measurements were first carried out in the liquid state at 2 20°Cand theii in the solid state at 25°C without changing the initial arrangement of the detector system and specimen. In each run, about 12000 counts per channel were accumulated at the position of the common peak. Background measurements were carried out with the same vessel before filling the specimen and subtracted from the total spectrum after proper normalization. Experimental data thus obtained were processed into a Compton profile J(q) following the procedure of Manninnen et al. [1] The generalized least squares method [2] was adopted as a deconvolution procedure. Fig. 1 shows Compton profiles J(q) observed for liquid and solid lithium. For small q-values a signifi-
1 8 16-
LITHIUM
1 4
.
:
10—
SOLID
.
~O8
~ O4~
o 2~— -
6
4
2
0 u )
2
1.
6
Fig. 1. Experimental Colnpton profilesf(q) for liquid and solid lithium metal. The dashed curve means the contribution of inner calculated in the impulse tion wingcore freeelectrons atom function by Clenienti 151. approxima0 ~
EXPERIMENT THEORY
.
cant difference can be should found between thepositron liquid and solid state. in This result be compared with that of experiments on angular in annihilation, which such a correlation significant difference has not been observed [3] On the other hand, the value of .1~~~(0) for solid lithium metal in this work lies below that reported by Wachtel et al. [4] which is per-
LIQUID .
1 2
0 05
..
..
—2
—
1
••••l•__
j
I 0
-
~ 1
2
.
,
haps due to the effect of multiple scattering, The difference between the Compton profiles J(q)
Fig. 2. Experimental and theoretical difference curves of Compton profiles, L~J(q)— ~liq (q) J 50~(q).See text. The error bars in the experimental difference curve mean the statistical error.
95
Volume 57A, number I
PHYSiCS LFTFLRS
of liquid and solid lithium metal is plotted in fig. 2. Fig. 2 can be thought to reflect a change of the deetronic structure of the conduction electrons in Iithium nietal upon melting, because the contribution of multiple scattering to Compton profiles is most likely the same in both states and will cancel. The solid line in fig. 2 denotes a theoretical diffetenee curve which is obtained by deconvoluting the theoretical function based upon the free electron model convoluted with the instrumental resolution function, using the same parameters as used to obtain experimental profiles. This theoretical curve is in good agreement with the experimental one, which suggests that the change of the electronic structure in lithium metal Upon melting can he qualitatively explained by the free
96
17 May 1976
electron model. Further experiments are in progress using thinner
samples to avoid the contribution of multiple scatter ing
References
Ill 121 131 141 151
S. Manninen, T. Paakkari and K. Kajantic, Phil. Mag 29 (1974) 167. P. Paatero, 5. Manninen and T. Paakkari, Phil. Mag. 30 AT. Stewart, Positron annihilation (Acadenm. Press, New York, 1967) p. 17. S. Wachtel, J. Fclsteiner, S. Kahane and R. Ophcr, Phys. Rev. B 12 (1975) 1285. I . Clcmenti, IBM J. Rcs. Develop. Suppl. 9 (1965) 2.