Strong $E2\mathrm{}$, $E3\mathrm{}$, $E4\mathrm{}$, and $E5\mathrm{}$ excitations of low-lying states in ${}_{}{}^{19}{}_{}{}^{}\mathrm{F}$ were observed in an electron scattering experiment. From the measured form factors the following radiative transition strengths to the ground state (in Weisskopf units) were extracted: ${\mathrm{}\left|M\right(E2\mathrm{}\left)\right|}^2=8.1\mathrm{}\pm 1.0$ (the 1.55-MeV ${\frac{3}{2}}^{+}$ state), 1.0±0.2 (4.56-MeV ${\frac{5}{2}}^{+}$); ${\mathrm{}\left|M\right(E3\mathrm{}\left)\right|}^2=11\mathrm{}\pm 3$ (1.35-MeV ${\frac{5}{2}}^{-}$), 15±4 (5.43-MeV ${\frac{7}{2}}^{-}$); ${\mathrm{}\left|M\right(E4\mathrm{}\left)\right|}^2=5.8\mathrm{}\pm 1.3$ (2.78-MeV ${\frac{9}{2}}^{+}$); and ${\mathrm{}\left|M\right(E5\mathrm{}\left)\right|}^2=16\mathrm{}\pm 7$ (4.03-MeV ${\frac{9}{2}}^{-}$). A fairly large transverse form factor was found for the 2.78-MeV ${\frac{9}{2}}^{+}$ state. The value of $B(M5, {\frac{9}{2}}^{+}\to \mathrm{g}.\mathrm{s}.\mathrm{})=(3.0\mathrm{}\pm 1.2)\times {10}^4{e}^2$ ${\mathrm{fm}}^{10}$ was extracted from the experimental data on the assumption that this transverse form factor resulted from $M5\mathrm{}$ excitation only. The experimental form factors and radiative transition strengths for positive-parity states are compared with theoretical values calculated using the rotation-particle coupling (RPC) model; good agreement is obtained for the states predominantly belonging to the ground-state band: the 0.197-MeV ${\frac{5}{2}}^{+}$, 1.55-MeV ${\frac{3}{2}}^{+}$, and 2.78-MeV ${\frac{9}{2}}^{+}$ states. It is found that RPC is essential, in particular, to the $E4\mathrm{}$ and $M5\mathrm{}$ transitions of the 2.78-MeV ${\frac{9}{2}}^{+}$ state. The $E3\mathrm{}$ transition strength of the 5.43-MeV ${\frac{7}{2}}^{-}$ state, as well as the 1.35-MeV ${\frac{5}{2}}^{-}$ state, is comparable with that of the octupole-vibrational state at 6.13 MeV in ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$.

NUCLEAR REACTIONS ${}_{}{}^{19}{}_{}{}^{}\mathrm{F}(e, e^{\prime })$, $E=134.5, 150, 250$ MeV; measured $\sigma (E ;\theta )$; deduced $B\left(\Lambda \right)$. ${\left(\mathrm{C}{\mathrm{F}}_2\right)}_n$ target. Compared with the rotation-particle coupling model.

• Received 20 January 1975

DOI:https://doi.org/10.1103/PhysRevC.11.1578