List of levels for 266MT

Author: Balraj Singh | Citation: Nucl. Data Sheets 156, 70 (2019) | Cutoff date: 31-Jan-2019

1982Mu15, 1984Mu07, 1988Mu15, 1989Mu16: ²⁶⁶Mt produced in ²⁰⁹Bi(⁵⁸Fe,n),E=5.15, 5.17 MeV/nucleon using SHIP separator at GSI. One decay chain reported by 1982Mu15 and 1984Mu07. Two additional decay chains were reported by 1988Mu15. Results also summarized in 1989Mu16 review article.

Event #1: 1982Mu15, 1984Mu07:

E_α1=11.10 MeV 4, Δt₁=5.0 ms, assigned to ²⁶⁶Mt

E_α2=1.14 MeV (escaped), Δt₂=22.3 ms, assigned to ²⁶²Bh

ε, Δt₃=12.9 s, assigned to ²⁵⁸Db, decays to ²⁵⁸Rf by ε

E_SF=232 MeV for dominant SF decay of ²⁵⁸Rf.

Event #2: 1988Mu15, 1989Mu16:

E_α1=5.8 MeV (escaped), Δt₁=4.8 ms, assigned to ²⁶⁶Mt

E_α2=10.21 MeV, Δt₂=13.2 ms, assigned to ²⁶²Bh

E_α3=1.4 MeV (escaped), Δt₃=9.3 s, assigned to ²⁵⁸Db

ε decay of ²⁵⁴Lr to ²⁵⁴No

E_α4=8.10 MeV, Δt₄=96 s, assigned to ²⁵⁴No, which α decays to ²⁵⁰Fm

Event #3: 1988Mu15, 1989Mu16:

Missed detection of α particles from the decay of ²⁶⁶Mt

E_α2=10.34 MeV, Δt₂=4.0 ms, assigned to ²⁶²Bh

E_α3=9.01 MeV, Δt₃=2.9 s, assigned to ²⁵⁸Db, , which α decays to ²⁵⁴Lr

1984Og03: ²⁰⁹Bi(⁵⁸Fe,n),E=5.5 MeV/nucleon using U400 cyclotron at JINR-Dubna, followed by off-line detection of long-lived daughters by radiochemical separation of Cm, Cf, Es, and Fm. Detected one track of ²⁵⁸Db (possibly originating from the α-α decay chain of ²⁶⁶Mt), and seven α decays from ²⁴⁶Cf (T_1/2=35 h +39-14).

1997Ho14 (also 1999He11 review article): ²⁶⁶Mt produced in ²⁰⁹Bi(⁵⁸Fe,n),E=287.6, 289.8, and 292.0 MeV using the UNILAC and SHIP at GSI. Measured excitation functions and production cross sections

History of 12 α-α-α decay chains observed by 1997Ho14:

Event #1:

E_α1=10814 keV, Δt₁=1.8 ms, assigned to ²⁶⁶Mt

E_α2=10213 keV, Δt₂=11.5 ms, assigned to ²⁶²Bh

ε, Δt₃=1.18 s - assigned to ²⁵⁸Db

Event #2:

E_α1=10661 keV, Δt₁=1.1 ms, assigned to ²⁶⁶Mt

E_α2=9834 keV, Δt₂=14.1 ms, assigned to ²⁶²Bh

E_α3=9387 keV, Δt₃=9.6 s, assigned to ²⁵⁸Db

Event #3:

E_α1=10576 keV, Δt₁=0.4 ms, assigned to ²⁶⁶Mt

E_α2=10379 keV, Δt₂=16.7 ms, assigned to ²⁶²Bh

E_α3=9189 keV, Δt₃=2.2 s, assigned to ²⁵⁸Db

Event #4:

E_α1=10561 keV, Δt₁=1.9 ms, assigned to ²⁶⁶Mt

E_α2=10443 keV, Δt₂=18.4 ms, assigned to ²⁶²Bh

E_α3=9380 keV, Δt₃=0.60 s, assigned to ²⁵⁸Db

Event #5:

E_α1=10809 keV, Δt₁=1.3 ms, assigned to ²⁶⁶Mt

E_α2=9763 keV, Δt₂=255 ms, assigned to ²⁶²Bh

ε decay, Δt₃=11.2 s, assigned to ²⁵⁸Db

Event #6:

E_α1=11739 keV, Δt₁=7.8 ms, assigned to ²⁶⁶Mt

E_α2=6.4 MeV (escaped), Δt₂=6.9 ms, assigned to ²⁶²Bh

E_α3=9179 keV, Δt₃=1.85 s, assigned to ²⁵⁸Db

Event #7:

E_α1=10456 keV, Δt₁=4.5 ms, assigned to ²⁶⁶Mt

E_α2=10372 keV, Δt₂=17.3 ms, assigned to ²⁶²Bh

E_α3=1.0 MeV (escaped), Δt₃=11.2 s, assigned to ²⁵⁸Db

Event #8:

E_α1=11306 keV, Δt₁=2.0 ms, assigned to ²⁶⁶Mt

E_α2=10001 keV, Δt₂=45 ms, assigned to ²⁶²Bh

E_α3=0.6 MeV (escaped), Δt₃=1.38 s, assigned to ²⁵⁸Db

Event #9:

E_α1=10484 keV, Δt₁=0.2 ms, assigned to ²⁶⁶Mt

E_α2=9902 keV, Δt₂=7.5 ms, assigned to ²⁶²Bh

ε decay, Δt₃=7.0 s, assigned to ²⁵⁸Db

Event #10:

E_α1=11682 keV, Δt₁=0.2 ms, assigned to ²⁶⁶Mt

E_α2=9831 keV, Δt₂=278 ms, assigned to ²⁶²Bh

E_α3=1.1 MeV (escaped), Δt₃=0.11 s, assigned to ²⁵⁸Db

Event #11:

E_α1=10859 keV, Δt₁=0.7 ms, assigned to ²⁶⁶Mt

E_α2=9803 keV, Δt₂=21.1 ms, assigned to ²⁶²Bh

Event #12:

E_α1=10848 keV, Δt₁=2.5 ms, assigned to ²⁶⁶Mt

E_α2=10143 keV, Δt₂=225 ms, assigned to ²⁶²Bh

E_α3=9064 keV, Δt₃=4.19 s, assigned to ²⁵⁸Db

1997Ho14 obtain T_1/2=1.7 ms +6-4 from the arithmetic mean of 14 decay times.

2009Ne02: ²⁰⁸Pb(⁵⁹Co,n),E=291.5 MeV from the 88-Inch Cyclotron at LBNL, using the Berkeley Gas Separator to separate the evaporation residues. Measured α decays and spontaneous fission events using a multiwire proportional counter (MWPC).

History of five correlated decay chains observed in 2009Ne02:

Event #1: Energy of the evaporation residue=21.6 MeV

E_α1=11260 keV, Δt_α1=15 ms, assigned to ²⁶⁶Mt

E_α2=3090 keV (escaped), Δt_α2=2 ms, assigned to ²⁶²Bh

E_α3=6880 keV (partial), Δt_α3=15.035 s, assigned to ²⁵⁸Db

²⁵⁴Lr decays by ε to ²⁵⁴No

E_α4=8060 keV, Δt_α4=26.990 s, assigned to ²⁵⁴No

E_α5=7400 keV, Δt_α5=25.812 min, assigned to ²⁵⁰Fm

Event #2: Energy of the evaporation residue=24.1 MeV

E_α1=2180 keV (escaped), Δt_α1=7 ms, assigned to ²⁶⁶Mt

E_α2=10380 keV, Δt_α2=38 ms, assigned to ²⁶²Bh

E_α3=1153 keV (escaped), Δt_α3=5.577 s, assigned to ²⁵⁸Db

E_α4=8450 keV, Δt_α4=17.908 s, assigned to ²⁵⁴Lr

Event #3: Energy of the evaporation residue=23.1 MeV

E_α1=4340 keV (escaped), Δt_α1=0.6 ms, assigned to ²⁶⁶Mt

E_α2=10060 keV, Δt_α2=1 ms, assigned to ²⁶²Bh

E_α3=9250 keV, Δt_α3=1.364 s, assigned to ²⁵⁸Db

E_α4=8490 keV, Δt_α4=9.013 s, assigned to ²⁵⁴Lr

E_α5=7780 keV, Δt_α5=16.610 s, assigned to ²⁵⁰Md

Event #4: Energy of the evaporation residue=23.1 MeV

E_α1=10670 keV, Δt_α1=0.2 ms, assigned to ²⁶⁶Mt

E_α2=8150 keV (partial), Δt_α2=185 ms, assigned to ²⁶²Bh

E_α3=1450 keV (escaped), Δt_α3=7.804 s, assigned to ²⁵⁸Db

²⁵⁴Lr decays by ε to ²⁵⁴No

E_α4=8050 keV, Δt_α4=9.412 s, assigned to ²⁵⁴No

E_α5=7570 keV , Δt_α5=36.260 min, assigned to ²⁵⁰Fm

Event #5: Energy of evaporation residue=23.1 MeV

E_α1=1140 keV (escaped), Δt_α1=0.5 ms, assigned to ²⁶⁶Mt

E_α2=10070 keV, Δt_α2=39 ms, assigned to ²⁶²Bh

E_α3=1440 keV (escaped), Δt_α3=8.786 s, assigned to ²⁵⁸Db

E_α4=8450 keV, Δt_α4=13.759 s, assigned to ²⁵⁴Lr

²⁵⁰Mo decays by ε to ²⁵⁰Fm

E_α5=7440 keV, Δt_α5=7.495 min, assigned to ²⁵⁰Fm

Possible isomerism in ²⁶⁶Mt: isomeric activity decaying by α is proposed by 1997Ho14 and 1999He11 in view of the large spread in measured Eα values (10.484 to 11.739 MeV) and mean lifetimes (ranging from 0.2 to 7.8 ms) for 14 events in 1997Ho14 (including two from 1988Mu15 and 1984Mu07) and five from 2009Ne02, and also existence of two α-decaying activities of ²⁶²Bh, α daughter of ²⁶⁶Mt. Also note a comment by 1997Ho14 that events #5, #10 and #12 were correlated to three α decays of ²⁶⁶Mt near 10.8 MeV, possibly decays from a level different from the other transitions. 2017Au03 (NUBASE-2016) adopted g.s. of ²⁶⁶Mt with T_1/2=1.2 ms 4, based on lifetime data from ten events in 1997Ho14; and isomer in ²⁶⁶Mt at 1140 keV 80 with T_1/2=6 ms 3, based on data from three events in 1997Ho14. 2017Au03 and 2017Wa10 did not refer to 2009Ne02 work where five additional events were reported. In the opinion of the evaluator, a definite evidence for an isomer in ²⁶⁶Mt is lacking, and further experiments on this isotope are warranted.

For theoretical studies, consult Nuclear Science References (NSR) database at NNDC, BNL for 44 primary references dealing with the half-lives and other aspects of nuclear structure in this mass region

Q-value: Estimated uncertainties (2017Wa10): ΔS(n)=550, ΔS(p)=310

Q-value: S(2p)=2670 350, Q(εp)=4260 390 (syst,2017Wa10). S(2n)=15510 (theory, 1997Mo25)

Q-value: 2018It04 deduced mass excess of ²⁶⁶Mt as 127803 keV 152 using Q(α) from 2017Wa10, where mass excess is given as 127962 keV 306 from systematic trend.

S(n)= 6790 keV SY	S(p)= 230 keV SY	Q(α)= 10996 keV 25
Reference: 2017WA10

E(level)	J^π(level)	T_1/2(level)	Comments
0		2.1 ms 7 % α > 75 % SF < 25	No evidence was found for ε or SF decay modes (2009Ne02,1997Ho14). The SF events detected in 1984Og03 were interpreted as being from ²⁵⁸Rf decay, the ε decay daughter of ²⁵⁸Sg, the α grand-daughter of ²⁶⁶Mt. From the systematics of SF decay half-lives, 1984Og03 suggested that ²⁶⁶Mt decays mostly by α. E(level): No evidence was found for ε or SF decay modes (2009Ne02,1997Ho14). The SF events detected in 1984Og03 were interpreted as being from ²⁵⁸Rf decay, the ε decay daughter of ²⁵⁸Sg, the α grand-daughter of ²⁶⁶Mt. From the systematics of SF decay half-lives, 1984Og03 suggested that ²⁶⁶Mt decays mostly by α.