I OFT ORNL P 1302 ' . --- Ti - - TFFFEE FREE MICROCOPY RESOLUTION TEST CHART NATIONAL BUREAU OF STANDARDS - 1963 OP utt. LEGAL NOTICE This report was prepared as an account of Government sponsored work. Neither the United States, nor the Commission, nor any person acting on behalf of the Commission: A. Makes any warranty or representa- tion, expressed or implied, with respect to the accuracy, completeness, or usefulness of the information contained in this report, or that the use of any information, appa- ratus, method, or process disclosed in this report may not infringe privately owned rights; or B. Assumes any liabilities with respect to the use of, or for damages resulting from the use of any information, apparatus, method, or process disclosed in this report. As used in the above, "person acting on behalf of the Commission” includes any em- ployee or contractor of the Commission, or employee of such contractor, to the extent that such employee or contractor of the Commission, or employee of such contractor prepares, disseminates, or provides access to, any information pursuant to his employ- ment or contract with the Commission, or his employment with such contractor. -2 لندرور CONF-650706-12.1 JUN 24 1965 wie Interaction or 350 keV Polarized Deutzons with Oriented 40%E0 Nuclei." R. Wagnez**, .D. :511er, eni T. Tanunc.; : 2 metional Laboratory, Cal Ridge, Tennessee, and H. Karshak, lat.:02:2. Su of Standards, Fascington, D. C. -LEGAL NOTICE - TW. raport me propun un account al Govern sponsored work. Kaldhor the tallad Bates, nor the Coulom, mor my porno keting a b old Contactos A. Kalles wynrrunty or reprimaution, exprewed or impued, nu repect to the sery- racy, complemevesa, or wehalos de buruation contatodu do raport, or d e were of may laloration, appunto, method, or process declosed to the report any of tables printoly omdraue; or D. Asmundo wy Handwas nu nospect to the weat, or for den neuing trou the umowy llor ullos, apointu, bathod, or proctus dixcloud la o report. Ao wond la the bbon, "perk. K au wall of the Court" include my ploys or contractor of the Countnetom, or employee ol much connecter, to the adut that ouch toployee or contractor of the couloulon, or employo al med contractor propurus. donntastes, or provides are to, may information power to Ms suployment of contract will the Counselor, or No reployment with much contractor. The interaction oz polarized and unpolarized 350 keV neutrons with oriented and woriented <ño nuclei vas invesüigated in order to search or a possible spi:-spin interaction and to study also the influence due to nuclear dezormation. A deformation effect in the total cross section of the orienteå tüzzet was fourà to be in quantitative agreement with a couzlei-channel calculation. The spin-spin interaction was found to be more than one cråer oſ magnitude smaller than the spin-orbit interaction for this nucieus. Tie ORL puised ană Bunched 3 MV Van de Graaff was used in conjunction with a time-02-1 light spectrometer. The Li' (0,n) reaction provided a scurce of 55% polarizeú, 350 Xev neutrons [i]. Using the National Bureau oï Standards üransportable He” zeirigerator [2] a single crystal of holmium metalï was ccoled to 0.31°K. An external magnetic field or 2.5 koe, which was obtained by a super- conducting spliï solenoid, was applied along one of the directions of easy zaznetization of the crystal. Due to the large hypertine interaction for coiwiw metal, large values for the nuclear polarization can be obtained. "Research jointly sponsorea oy the U. S. Atomic Energy Commission under contract with union Carbide Corporation and the National Bureau of Stänäanas. "Pemeri zdáress: mysikalisches Institui. der Universitat Basel, Deser, Sizewid. . . * !T- -www.. 03 :zatežel to Di. S. Legvold and FEREASEFY 5. Spedding for Ciaomi Caryo *. o ATENT CLEARANCE OETIINIT. REBASEIPY 5. om THE PUBLIC IS AC730%! . "ROOCHURES ARE ON FILE liv T:.:. : SECTION, - - For the values oi temperature and magnetic field given above and correcting for the demagnetining rield in the sample, a value of approximately 15% was cötaineå for the nuclear polarization parameter < In My The subscript Hidicates that this parameter was evaluated with respect to the direction or the applied liela. The differential cross-section for unpolarized, 350 eV neutrons, elastically scattered inom unozierted 10370 nuclei was measured and the cata were corrected for multiale scattering. The differential cross-section is congea viti üzcozy in is. I and the areement is seen to be satis- Pactory. The theoretical curve was obtained by computing first the shape- elastic cross-section using a FORTRAN coke [3] which couples the 7/2 (sound) and the 9/2" (Tirst excited) channels, and then adding the compound- elasüic cross-section obtained by an appropriately moäiliea Hauser-Fesibach calculation, Tae optical model po'üential useå was V(7,0.9) = - (V + 10) (2 + 20)-2 - 414,75 (1 + 2+)-2 - VsC6D) (4,2/2R Je*(1 + 21)-2 with é' = exto4 (-3(0,0,0,1)/2}; R(0,0,0z) = R. (1 + $¥20 [09)), ēs = exp{{3-R18,0,0,))/7}; R(9,0,0.7) = Ř (2 BY2060*)), R = 747/3, R = 7 42/5, and the parameter values are given in fig. 1. 411 of these values are quite reasonable; in particular the nuclear deformation parameter is in agreement with results from Coulozb-excitation and Photo-neutron experi- menis. Tae total cross-section of unoriented toho was measured in the energy range from 300 to 400 icey. The data are compared with the coupled-channel calculation in iig. 2. The parameters used for the theoretical lit are the same as those wäich fitted the elastic angular distribution. - 2 . that can ORVA VALLI j wy; stales comis V 4: WY - - me. Is www - toilronn moms - · 0 0 0 40 0 00 180 MOM MO Fig. ļ. Differential elastic scattering cross section of unoriented >Ho nuclei for unpolarized 350 keV neutrons QANLONG 64-2269R - -- fc-:- THEORY + - opſborns) 300 400 320 340 360 380 En(KGV) Totol Cross-Section, Ho 65 Fig. 2. Total cross-section of unoriented to?HO for 300 to: 400 keV neutrons. The theoretical curve is discussed in the text. The optical model parameters used are those given ; m fig .ܐ ' - 3. To investigate the spin-spin interaction, measurements were made of the transmitted neutron intensities with the target nuclei polarized alternately parallel and anti-parallel to the direction of neutron polari. zation. For the values of the neutron and nuclear polarization given above, and for the measured total cross-section of 7.94 barns, the observed change in intensity of (-0.11 + 0.32)% implies a change in cross-section of (+30 + 85) mb, where the plus sign corresponds to a larger cross-section for the parallel orientation. If one adds a spin-spin interaction term -V. (0.1){1,+ exp[ (r - r 44/3)/a]}-] to (1), the total cross-sections for the parallel, 017, and that for the antiparallel polarizations only, are different and the difference Apoy = 077 - 076t is plotted in fig. 3 as a friction of VasComparing with the experimental 40001° given as the shaded area in fig. 3 we can conclude that Ve satisfies the following relation: -0.13 MeV < V < 0.28 MeV SS To investigate the effect of nuclear deformation, a transmission measurement was made to determine the change in total cross-section between a target of highly oriented nuclei (T = 0.34°K, H = 2.5 koe, fg = 0.31), . and a target of almost unoriented nuclei (T = 4.2°K, I = 2.5 koe, I, = 0.005). The nuclear alignment parameter, In, is given with respect . ORNL - OWG 64-22708 SPIN-SPIN EFFECT semor (THEOR) Οσοι (EXP) Acor,lokimo) - 0.13 A : I . -0.6 0.6 -0.4 -0.2 0 0.2 0.4 SPW-SPW POTENTIAL STRENGTH (MOVI Fig. 3. Cross-section splitting due to a spin-spin interaction and comparison with experiment - 4. to the direction defined by the hyperfine field at the nucleus. These directions coincide with the directions of the atomic moments. The transmission of the target decreased by (1.3 $ 0.47% for the higher alignment value. This corresponds to a cross-section increase, A copy of (350 $ 100) mb. The theoretical 10 cop was computed also in the coupled-channel calculation, and the result is compared with experiment in fig. 4. There, 40 ger is given as a function of , for W, = 3.0 and 5.0 Mev. (V was adjusted to fit the data of figs. 1 and 2 for each value of 7. As is seen, good agreement with the experimental 40 def is obtained if W = 3.0 MeV is taken. It is also seen that we can exclude W, = 5.0 MeV, a feature that could not be achieved, if only the data of figs. 1 and 2 were :'{tted. In conclusion, our data are consistent in each comparison with the predictions of the coupled-channel calculation. The diversity of the data provides rather strong restrictions on the parameters specifying the optical and structural properties of this deformed aucleus. ONKLON 64.6473 DE FORMATION EFFECT . .. do not imo) .. .. 5.0 MOV .. .. 125 630 135 ola • Fig. 4. Deformation splitting of the total cross-section compared with theoretical results References Tit A. J. Elwyn and R. O. Lane, Nucl. Phys. 31 (1962) 78. (2) E. Ambler, R. B. Dove' and R. S. Kaeser, Advan. Cryogenic Eng. (Plenum Press, 1963) p. 443; E. Ambler, F. S. Fuller and H. Marshak, Phys. Rev. 138B (1965) 217. (3) T. Tamura, contributed paper A4 to the Topinal Conference on Nuclear Spectroscopy with Direct Reactions, 9-11 Masch, 1964, ANL-6848. END DATE FILMED 18 / 27 /65 Um "