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 WWW TUNL    ## 11Be (1968AJ02)

(See Energy Level Diagrams for 11Be)

GENERAL: See Table 11.1 [Table of Energy Levels] (in PDF or PS).

Mass of 11Be: The Q-value of the 9Be(t, p)11Be reaction is given as Q = -1.164 ± 0.015 MeV by (1962PU01) (based on 12C(t, p)14C*). This value has been adjusted by (1965RY01) to -1.170 MeV, leading to M - A for 11Be = 20.181 ± 0.015 MeV (relative to 12C) (1965MA54).

See (1960TA07, 1960TA1C, 1961DO03, 1966RO11, 1967DE1V). The ground state of 11Be has even parity (1964AL22).

 1. 11Be(β-)11B Qm = 11.513

The decay proceeds to the 11B states at 0, 2.12, 6.79 and 8.00 MeV (Jπ = 3/2-, 1/2-, 3/2+, 3/2+, respectively); the half-life is 13.68 ± 0.14 sec. The nature of the decay indicates even parity, Jπ = 1/2+, 3/2+ or 5/2+ for 11Beg.s. (1961DO03, 1964AL22): see 11B.

 2. 9Be(t, p)11Be Qm = -1.170

Proton groups have been observed corresponding to seven states of 11Be: see Table 11.2 (in PDF or PS) (1962PU01). Angular distributions measured at Et = 6, 10 and 14 MeV do not show a clear stripping pattern for the ground-state protons. At Et = 14 MeV, the distribution of protons corresponding to 11Be*(0.319) exhibits an L = 2 pattern indicating Jπ = 1/2-, 5/2- or 7/2- (1962PU01, 1964HI08). (1960TA07) suggest Jπ = 1/2+ and 1/2- for the ground and first excited states, respectively. The dimensionless reduced widths θ2n for Ex = 1.8, 2.7 and 3.4 MeV indicate l = 0, 1 or 2 decay to 10Be + n, Jπ = 1/2±, 3/2± or 5/2+ (1962PU01). See also (1968HO1F).

 3. 9Be(6He, α)11Be Qm = 6.343

See (1967ST21) and 15C.

 4. 11B(n, p)11Be Qm = -10.731

At En = 14.8 MeV, σ(nα)/σ(np) = 10.0 ± 1.5 (1958NU40).

 5. 11B(γ, π+)11Be Qm = -151.09

See (1962DY1A, 1963NE07).  