Various features of the spectral profil e of an x-ray on e ca n be meas ured with an uncertainty whi ch is onl y a s mall fraction of the observe d line width. With rece nt improve me nts in me asure me nt tech· niqu es, statisti cal errors due to th e ra ndom Au ctuations of th e intensities in counter recordin gs may beco me signifi cant. The prese nt study co nsiders th e effec t of s uch errors on se ver al features of the line profil e whi ch could be used for definition of its wave length. These may be broadly classified into three groups, viz , th e peak, the centroid , and the median. In th e prese nt an alysis the s tatistical eu ors associated with these features are co mpared theore ticall y, with the ass umption of negligible error in angul ar meas ureme nt. Certai n sys temati c errors are also brie Ay exa min ed. The effects of trun cation range, asymmetry, and bac kground intensit y are co ns idered, as well as possibl e optimi z.ation of th e data-taking procedu re.In general, fT , the standa rd dev iation of the wave length , is give n by fT/W = F/(lvn' /2, where IV is the full width at half-maximum intensity, Iv the peak intensit y, T the total countin g ti me, and F a dim ensionless fac tor of the order of unity. Thu s. F may be rega rd ed as a fac tor of me rit for comparing th e various cases, a low valu e of F bein g des irable . Wh en the form of th e on e pro fil e is known a priori , it is usually bes t to make use of thi s kn owl edge; e.g. , a Lore ntzi an ca n be thu s fitted with F "" 0.8 for any of the three wavelength features. Us in g optimize d truncation ranges a nd in cludin g the error in locating end points, one obtain s ap prox im ate ly thi s sa me F for the ce ntroid or medi an even without prior knowl edge of the profil e. In th e latt er case the val ue of F for the pea k usuall y ra nges from abo ut 1.6 to 2. 1. Howeve r, the peak is less subject to c ertain syste mati c errors a nd is prefera ble from th e view point of sim plic ity and hi storical precede nt. It is reco mmen ded that use of the pea k be co ntinued at present; further stud y of th e proble m from the viewpoi nt of atomi c e nergy level interpretation would be desirable.
The decay of 20.90-min Pm has been studied with Ge(Li) and NaI(Tl) p-ray detectors in a variety of singles and coincidence configurations, including Ge(Li)-Ge(Li) two-parameter "megachannel" coincidence experiments, anticoincidence experiments, and pair (y~-y) experiments to determine the relative P+ feedings, Fifty-two y rays were identified from this decay, and 43 of these (& 99%%up of the y intensity) were placed in a decay scheme containing 23 levels in 4 Nd, J~a ssignments or l.imits were made for all of the states, The structures of the lower-lying states in Nd are discussed in terms of the shell model, and possible structures are also suggested for many of the higher-lying states. We compare our results with those of previous studies and also with particle-transfer data, RADIOACTIVITY Pm; measured E&, I&, yy coin, y y coin, deduced nE, 4~Nd deduced levels, J; x. the particle transfer experiments. ' ' II. SOURCE PREPARATION AND IDENTIFICATIONMost of the 20.9-min "'Pm activity was produced by the '4'Nd(P, 2n) "'Pm reaction on targets of Nd, O"with the neodymium enriched to =90% '"Nd. The bombarding times were typically 1-2 min with =1-p,A beams of 24-MeV protons from the Michigan State University sector-focused cyclotron. Counting began within 2 min of the end of the bombardment, and each source was not counted longer than 50 min.A study of the excitation function was made by varying the incident beam energy in = 3-MeV steps from below the 14-MeV threshold of the (P, 2n) reaction to 30 MeV, which is 5 MeV above the 952
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
customersupport@researchsolutions.com
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.