Comment on "Transverse Wobbling in 135 Pr [Phys. Rev. Lett. 114, 082501 (2015)]"
CComment on “Transverse Wobbling in
Pr [Phys. Rev. Lett. 114, 082501 (2015)]”
S. Guo
1, 2 CAS Key Laboratory of High Precision Nuclear Spectroscopy,Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou 730000, China School of Nuclear Science and Technology, University of ChineseAcademy of Science, Beijing 100049, People’s Republic of China (Dated:)In [J. T. Matta et al., Phys. Rev. Lett. 114, 082501 (2015)] a transverse wobbling band wasreported in
Pr. The critical experimental proof for this assignment is the E2 dominated linkingtransitions between the wobbling and normal bands, which are supported by two experiments per-formed with Gammasphere and INGA. However, the M1 dominated character cannot be excludedbased on the reported experimental information, indicating that the wobbling assignment is stillquestionable.
PACS numbers: 21.10.Re, 21.60.Ev, 23.20.Lv, 27.60.+j
The present comment exposes some concerns on thereported experimental proofs on the declared wobblingband in
Pr [1].Angular distribution curves can be estimated assum-ing appropriate values for the mixing ratio ( δ ) and thealignment parameter ( σ/I ). From the comparison withthe experimental results, it is possible to deduce suitablemixing ratios to get a good agreement between estimatedand experimental results. Usually, equally good agree-ments can be achieved with two mixing ratios | δ | > | δ | < δ and δ , to the experimental results with convinc-ing errors. However, in the commented article [1], foreach M /E δ or δ was plotted and compared with pure M δ = 0), leading to a false belief that the correct solu-tion for the mixing ratio is reliably established since thecurve for δ = 0 is far apart from the experimental points.Based on the reported results from angular distributionmeasurements (Fig. 2 in Ref. [1]), we added the curvewith the other fitted solution to each figure (see the greencurves in Fig. 1). Actually, both the two curves with δ and δ fit with the experimental points well within thereported errors.In the commented article [1], positive asymmetrieswere deduced from the linear polarization measurements,and were regarded as a clear proof to identify the twotransitions of 747.0 and 812.8 keV as predominately elec-tric in nature. However, a positive asymmetry does notexclusively imply a predominantly electric character for∆I=1 M /E σ /I. For the twotransitions of 747.0 and 812.8 keV, the estimated polar-ization values are positive with both δ and δ (see Fig.2). Therefore both δ and δ cannot be ruled out by .
747 keV Exp. δ=0δ =-0.5δ =-1.54 Exp. δ=0δ =-0.64δ =-1.24
813 keV Exp. δ=0δ =-1.74 δ '=-0.16 δ =-0.46
594 keV755 keV Exp. δ=0δ =-0.36δ =-2.38 C oun t s / θ(°) FIG. 1. (Color online) Estimated angular distribution curvesand experimental results for the linking transitions in
Pr.For the 594-keV transition in
Pr, δ = -0.46 is deducedfrom the curve marked with δ (cid:48) = -0.16 in Ref. [1], thereforetwo corresponding curves are both plotted. the reported experimental results in Ref. [1]. Consid-ering the polarization values are slightly different for δ and δ , the real solution can only be decided by an extraprecise analysis. To deduce the polarization values, thecalibrated polarization sensitivity and deduced σ/I pa-rameters for each transition in the INGA measurementshould be taken into account, which were not mentionedin the Ref. [1].In summary, it is insufficient to declare a wobblingband based on the reported experimental proofs in Ref.[1]. Further experimental researches are necessary toclarify the nature of this band.The author thanks Professor C. M. Petrache for use-ful discussions. This work has been partly supported bythe National Natural Science Foundation of China, undercontract No. U1932137. a r X i v : . [ nu c l - e x ] J a n - - - - - - - - Mixing ratio P o l a r i za ti on σ / = I σ / = I17 2 → /
21 2 → / δ = . -1 24δ =- =- .
1 54δ =- - - - FIG. 2. (Color online) The polarization coefficients as func-tions of mixing ratios with different σ /I parameters. [1] J. T. Matta, U. Garg, W. Li, S. Frauendorf, A. D.Ayangeakaa, and D. Patel et al. , Phys. Rev. Lett.114