Log ft values in Beta Decay Filip G. Kondev kondev@anl.gov 2nd Workshop for DDEP Evaluators, Bucharest, Romania May 12-15,2008

Some useful references Books “Week interaction and nuclear beta decay”, H.F. Schopper, 1966 “Handbook of nuclear spectroscopy”, J. Kantele, 1995 “Radiation detection and measurements”, G.F. Knoll, 1989 “Alpha-, Beta- and Gamma-ray Spectroscopy”, Ed. K. Siegbahn, 1965 Journal Articles W. Bambynek et al., Rev. Mod. Phys. 49 (1977) 77 N.B. Gove and M.J. Martin, Nuclear Data Tables 10 (1971) 205 S. Raman and N.B. Gove, Phys. Rev. C7 (1973) 1995 B. Singh et al., Nuclear Data Sheets 84 (1998 487 Plenty of information available on the Web

Introduction b+: p  n + e+ + n EC: p + e-  n + n ~ Beta Decay: universal term for all weak-interaction transitions between two neighboring isobars Takes place is 3 different forms b-, b+ & EC (capture of an atomic electron) b+: p  n + e+ + n EC: p + e-  n + n b-: n  p + e- + n ~ a nucleon inside the nucleus is transformed into another

Classification of b decay transition Iipi Eb Ifpf Lb = n defines the degree of forbiddenness (n) allowed forbidden when Lb=n=0 and pipf=+1 when the angular momentum conservation requires that Lb=n >0 and/or pipf=-1

Classification of allowed decay Fermi Gamow-Teller 0+ 0+ Eb Eb 0+ 1+ 2+ mixed Fermi & Gamow-Teller Eb 2+

Order of forbiddenness Classification of b decay transitions Type of transition Order of forbiddenness DI pipf Allowed 0,+1 +1 Forbidden unique 1 2 3 4 . k2 k3 k4 k5 -1 Forbidden 0, k1

Some useful empirical rules The fifth power beta decay rule: the speed of a b transition increases approximately in proportion to the fifth power of the total transition energy (if other things are being equal, of course) Eb If Ii depends on spin and parity changes between the initial and final state additional hindrance due to nuclear structure effects – isospin, “l-forbidden”, “K-forbidden”, etc.

b decay lifetime partial half-life of a given b- (b+,EC) decay branch (i) g – week interaction coupling constant pe – momentum of the b particle We – total energy of the b particle W0 – maximum energy of the b particle F(Z,We) – Fermi function – distortion of the b particle wave function by the nuclear charge Cn – shape factor Z – atomic number

b decay Hindrance Factor statistical rate function (phase-space factor): the energy & nuclear structure dependences of the decay transition contains the nuclear matrix elements

N.B. Gove and M. Martin, Nuclear Data Tables 10 (1971) 205 Log ft values coming from calculations coming from experiment Decay Mode Type DI (pipf) log f b- EC + b+ allowed 0, +1 (+) 1st-forb unique k2 (-) N.B. Gove and M. Martin, Nuclear Data Tables 10 (1971) 205

Log f ENSDF analysis program LOGFT – both Windows & Linux distribution http://www.nndc.bnl.gov/nndcscr/ensdf_pgm/analysis/logft/ LOGFT Web interface at NNDC http://www.nndc.bnl.gov/logft/

Log t What we want to know accurately T1/2, Ig, aT & d In = 0.69(10) Out = 0.69(10) (net)

Rules for Spin/Parity Assignments ~1000 cases There are only a few cases where unambiguous assignment can be made “pandemonium effect” – neutron rich nuclei – log ft is a just lower limit! needs to know the decay scheme and its properties accurately!

Log ft values – latest review ~3900 cases -> gives centroids and widths B. Singh, J.L. Rodriguez, S.S.M. Wong & J.K. Tuli

Implications for DDEP evaluations from systematics from calculations from experiment

…but be careful, nuclear structure is important w K~0 j=R K=7 j1 j2 j large angular momentum re-orientation First forbidden  5 < log ft <10 T1/2 =3.8x1010 y 0+ 2+ 4+ 6+ 8+ 7- log ft =20 log ft =19 K-forbidden decay