
^{9}B (1974AJ01)(See Energy Level Diagrams for ^{9}B) GENERAL: See also (1966LA04) and Table 9.9 [Table of Energy Levels] (in PDF or PS). Model calculations: (1966BA26, 1966EL08, 1967ST1C, 1971CO28, 1972LE1L, 1973HA49). Special levels: (1966BA26, 1966EL08, 1967BA59, 1967ST1C, 1969HA1G, 1970TO1E, 1971CO28, 1971LI30, 1972BE1E). Astrophysical questions: (1970BA1M). Other topics: (1967CA17, 1967CH1H, 1970SA05, 1972AN05, 1972HA57, 1972CA37, 1972LE1L, 1972PN1A, 1973JU2A). Ground state properties: (1966BA26, 1966EL08, 1968PE16, 1969HE1N, 1969JA1M, 1969LE1D, 1971AU1G, 1972LE1L).
The total cross section for reaction (a) has been measured from threshold to E(^{3}He) = 3.5 MeV: it increases monotonically reaching the value 4.3 mb at 3.5 MeV (1973MCZW). No structure is observed in the n_{0} excitation curve for E(^{3}He) = 4.0 to 5.7 MeV (1967VA24). The yield of ^{8}B has also been measured for E(^{3}He) = 8.9 to 26.5 MeV (1973MA24). See also (1966FA1A) and ^{8}B. The excitation functions for protons leading to ^{8}Be*(0, 2.9) [p_{0}, p_{1}] have been measured for E(^{3}He) = 0.9 to 17 MeV (reaction (b)). Resonances are reported at E(^{3}He) = 1.6 MeV (Γ = 0.25 MeV) [1.68 MeV: (1969VI05). J^{π} = 3/2^{} or 5/2^{}] and 3.0 MeV (Γ = 1.5 MeV) (1956SC01). Above 5 MeV, the p_{0} yield at 0° increases monotonically with energy to E(^{3}He) = 17 MeV (1965FL03). Polarization measurements are reported at E(^{3}He) = 1.4 to 2.0 MeV (1966SI1C, 1971SI1J; p_{0}, p_{1}). See also (1970GA1G) and ^{8}Be. The yields of 0.43 and 0.48 MeV γrays (reaction (c)), measured for E(^{3}He) = 0.5 to 1.3 MeV, are reported to show the excitation of ^{9}B*(17.20 ± 0.02) with Γ = 110 ± 30 keV, J^{π} = 1/2^{+}, 3/2^{+}; T = 1/2 (1970AL25). See also ^{7}Be. Excitation functions for ground state tritons (reaction (d)) have been measured for E(^{3}He) = 10 to 16 MeV (1969NU1A) and 23.3 to 25.4 MeV (1972GI07). See also ^{6}Be. Differential cross sections have been measured at several angles for the ^{3}He groups to ^{6}Li*(0, 2.19) (reaction (e)) for E(^{3}He) = 23.3 to 25.4 MeV (1972GI07). See also ^{6}Li.
Angular distributions at E_{α} = 8.0, 10.0, 12.0 and 14.0 MeV all display strong forward peaking (1963ME08). At E_{α} = 14.4 MeV, neutron groups are observed to ^{9}Be*(0, 2.4): the upper limit of the cross section to a state at ≈ 1.7 MeV is 100 μb/sr or < 0.1 of the ground state group (1964BA29). See also ^{10}B.
Angular distributions of the t_{0} group have been measured for E(^{6}Li) = 4.0 to 5.5 MeV and at 7.35 and 9.0 MeV. No evidence was observed for a group corresponding to ^{9}B*(1.6) (1966KI09).
For E(^{3}He) to 12.5 MeV this reaction populates ^{9}B*(0, 2.4, 2.8, (7.0)) (1963DU12) and levels at 12.06 ± 0.06 [0.8 ± 0.2], 14.01 ± 0.07 [0.39 ± 0.11], 14.670 ± 0.016 [ < 0.045], 16.024 ± 0.025 [0.180 ± 0.016], 17.19 and 17.63 MeV [widths in brackets] (1964DI1A, 1965DI03). (1967BA59) report Q = (5306 ± 5) keV and therefore E_{x} = 14.659 ± 0.005 MeV (based on Q_{m}). ^{9}B*(14.66) is the first T = 3/2 state in ^{9}B (1965DI03). It γdecays to ^{9}B*(0, 2.4, 2.8) with branching ratios which appear to be similar to those for the analog state in ^{9}Be: see Table 9.6 (in PDF or PS). Assuming that the Γ_{γ} for both T = 3/2 states in ^{9}Be, ^{9}B are the same, the total Γ for ^{9}B*(14.66) is then ≈ 80% of that for ^{9}Be*(14.40): 260^{+90}_{120} eV (1971AD01) [corrected for revised value of Γ of ^{9}Be*(14.40)]. The ratio Γ_{p}_{0}/Γ_{γ0} < 1.5, Γ_{p}_{1}/Γ_{γ0} = 13.9 ± 2.1 [Γ_{p0} is the width for decay of ^{9}B*(14.66) to the ground state of ^{8}Be; Γ_{p}_{1} is that for decay to ^{8}Be*(2.9)]. Assuming Γ_{γ0} for ^{9}B*(14.66) = 6.9 ± 0.5 eV [the value for the analog state in ^{9}Be: see Table 9.6 (in PDF or PS)], Γ_{p0} < 10 eV, Γ_{p1} = 96 ± 20 eV (1972AD04). See also (1971AD1C). Angular distributions have been reported for E(^{3}He) = 1.56 to 5.27 MeV (1966DI04; n_{0}) and 3.1 MeV (1970GU08; n_{0}). (1970GU08) find that a structure in the neutron spectrum which might correspond to ^{9}B*(1.5) is really due to sequential decay of ^{9}Be*(11.8) to ^{8}Be(0). They also report a ^{9}B state with E_{x} = 4.8 ± 0.1 MeV, Γ = 1.0 ± 0.2 MeV. See also (1970LI1Q), (1969BA1Z) and ^{10}B.
For E_{d} = 0.75 to 1.70 MeV, resonances in the yields of protons are observed at E_{d} = 0.900 ± 0.025 MeV (p_{0}, p_{2.4}) and 1.475 ± 0.010 MeV (p_{2.4} only) with Γ_{cm} = 120 ± 40 and 71 ± 8 keV, respectively [^{9}B* = 17.19 and 17.64 MeV] (1960KA17). See (1972PA1C) for astrophysical considerations.
A high resolution experiment at E_{p} = 20 MeV shows the population of ^{9}B*(0, 2.4) and is consistent with the excitation of ^{9}B*(2.8) [Γ ≈ 0.3 MeV] and ^{9}B*(7.0) [Γ > 1 MeV]. No other states are excited for E_{x} < 7.1 MeV (1970AN07). (1972AR22) report E_{x} = 3.09 ± 0.10 MeV. Additional states have been reported by a number of groups: see (1966LA04) for earlier references and (1967SL04, 1970CL01). The width of the ground state is 540 ± 210 eV (1964TE01). Angular distributions have been measured at E_{p} = 3.5 to 10.9 MeV (1965WA04), 6.8 MeV (1967DR08), 8 to 14 MeV (1960SA03), 18.5 MeV (1964AN1B) and 30.3 and 49.3 MeV (1970CL01). See also (1967BO1D, 1969JU1A, 1969VE02, 1970WI1B, 1971BE46, 1971CA1F, 1972CA1Q, 1973WA28), (1966LA04) and (1966PA1H, 1968TH1H; theor.).
Angular distributions have been reported at E(^{3}He) = 3.0 to 3.8 MeV (1969OR01; t_{0}), 5.0 to 9.0 MeV (1967EA01; t_{0}), 5.7 MeV (1959HI69; t_{0}), 10 MeV (1967CR04; t_{0}, t_{2.4}), 20 to 27.8 MeV (1969OP1A, 1970OP1B; t_{0}, t_{2.4}) and 25 MeV (1960WE04; t_{0}, t_{2.4}). At E(^{3}He) = 39.8 MeV ^{9}Be(0) is very stongly excited and ^{9}B*(2.4, 14.7) are also observed. There is some indication that other known ^{9}B states are also populated (1969BA06). See also ^{12}C in (1975AJ02) and (1970CA28).
At E(^{6}Li) = 30.8 and 31.8 MeV the ground state of ^{9}B is strongly excited. ^{9}B*(2.4) is also observed (1970CH19, 1971CH1B). A partial angular distribution for the ground state transition is reported at the higher energy by (1971CH1B).
Several groups of delayed protons are observed indicating the involvement of a number of ^{9}B states: see Table 9.10 (in PDF or PS) (1972ES05). It is not possible to determine ft values since some of the ^{9}B states involved in the ^{9}C decay may decay via ^{5}Li + α: see (1972ES05).
See ^{10}B.
At E_{p} = 33.6 MeV (1968KU04, 1970KU1D) and 155.6 MeV (1969BA05) deuteron groups are observed to ^{9}B*(0, 2.4, 7.0, 11.7, 14.7). All have angular distributions characteristic of l_{n} = 1 and therefore odd parity and J = (3/2, 5/2, 7/2, 9/2): see Table 9.11 (in PDF or PS). There is some evidence also for the population of ^{9}B*(2.8, 18.4) (1968KU04, 1969BA05). Angular distributions have also been reported at E_{p} = 49.5 MeV (1970SQ01; d_{0}, d_{2.4}, d_{11.7}). See also (1968KR02), (1966LA04) and (1969TO1A; theor.).
Angular distributions have been measured at E_{d} = 11.8 MeV (1966BA21, 1967FI07; t_{0}, t_{2.4}) [S for ^{9}B*(0, 2.4) = 0.80 and 0.64, respectively], 13.5 MeV (1964FU15; t_{0}) and 28 MeV [(1968GA13; t_{0}); (1971IN1C; t_{0}, t_{2.4} (partial)]. See also (1971WA1K, 1972WA1M) and (1966BA1X, 1971BO50; theor.).
Alpha particle spectra show the excitation of ^{9}B*(0, 2.4, 2.8, 11.8): see (1966LA04). Measurements by (1968KR02) determine E_{x} = 2.361 ± 0.005 and 2.788 ± 0.030 MeV, Γ = 81 ± 5 and 548 ± 40 keV, respectively [see Table 9.11 (in PDF or PS) in (1966LA04) for other values]. There is some evidence for a state with E_{x} ≈ 1.6 MeV, Γ ≈ 0.7 MeV, but it is not conclusive, in agreement with the older work [see (1960SP08, 1962BA1C)]. No evidence is found for any narrow levels in ^{9}B with Γ ≤ 100 keV and 4 < E_{x} < 7 MeV: the upper limit to the intensity of the corresponding αgroup is 1% of the intensity of the group to ^{9}B*(2.4) (1968KR02). Angular distributions have been determined at E(^{3}He) = 5.5 MeV (1966CA02; α_{0}) and 33.7 MeV (1971SQ03; α_{0}, α_{2.4}, α_{11.8}). DWBA does not seem to give a good description of the transition to ^{9}B*(11.8) (1971SQ03). In reaction (b) study of the decays of ^{9}B*(2.4, 2.8) shows that ^{9}B*(2.4) decays < 0.5% by proton emission to ^{8}Be(0) [θ^{2}_{f} < 5.1 x 10^{3}] [it decays to ^{5}Li(0) by αemission] while the second state, E_{x} = 2.71 ± 0.03 MeV [Γ = 0.71 ± 0.06 MeV] decays almost 100% by that channel [θ^{2}_{d} = 0.74] (1966WI08). (1966WA16) find Γ = 1.1 ± 0.2 MeV for ^{9}B*(2.8) and suggest J = 1/2 for this state [see, however, (1960SP08)]. No other excited states of ^{9}B with 3.5 < E_{x} < 9.5 MeV decay by proton emission to ^{8}Be(0) (1968KR02). See also (1970BE1F, 1971FO1E) and (1968TA1M; theor.). See also ^{8}Be, and ^{13}N in (1976AJ04).
See (1968OK06).
At E_{p} = 45 MeV angular distributions have been obtained for the triton groups to ^{9}B*(0, 2.36, 12.06, 14.01, 14.66, 16.02). In addition the spectra show some indication of the groups corresponding to ^{9}B*(7.0, 17.19, 17.63). New T = 1/2 states are reported at E_{x} = 15.29 ± 0.04 and 15.58 ± 0.04 MeV (1971HA10). See also (1971KA04; theor.) and reaction 41 in ^{9}Be.
Angular distributions of ground state αparticles have been measured at E_{p} = 14.0 to 17.2 MeV (1969KO1D), 19.1 to 44 MeV (1967AC01, 1969GA03, 1970GU06, 1971GU23), 38.5, 41.6 and 44.5 MeV [also partial backangle measurements at E_{p} = 30.5, 32.0, 33.0, 34.5 and 39.5 MeV] (1966CR05, 1967CR05, 1968LI1E) and at E_{p} = 54.1 MeV (1972MA21). Alpha groups are also observed to ^{9}B*(2.3, 2.9 ± 0.2, 6.97 ± 0.06): see (1955RE16, 1962MA40, 1964BA29, 1972MA21). See also (1966LA04). The angular distribution to ^{9}B*(6.97) is consistent with J^{π} = 7/2^{}; Γ ≈ 2 MeV (1972MA21: E_{p} = 54.1 MeV). For reaction (b) see (1972MA62) and (1966LA04). See also ^{12}C in (1975AJ02) and ^{13}N in (1976AJ04).
Angular distributions of ^{6}Li ions have been obtained at E(^{3}He) = 28 MeV (1971KL1E), 30.0 and 40.7 MeV (1972OH01) and 35.7 MeV (1969ZE1A, 1970FO1D).
