  Excited states in 13O were investigated using inelastic scattering of an
E/A=69.5-MeV 13O beam off of a 9Be target. The excited states were identified
in the invariant-mass spectra of the decay products. Both single proton and
sequential two-proton decays of the excited states were examined. For a number
of the excited states, the protons were emitted with strong anisotropy where
emissions transverse to the beam axis are favored. The measured proton-decay
angular distributions were compared to predictions from distorted-wave
born-approximation (DWBA) calculations of the spin alignment which was shown to
be largely independent of the excitation mechanism. The deduced $^{13}$O level
scheme is compared to ab initio no-core shell model with continuum (NCSMC)
predictions. The lowest-energy excited states decay isotropically consistent
with predictions of strong proton 1s1/2 structure. Above these states in the
level scheme, we observed a number of higher-spin states not predicted within
the model. Possibly these are associated with rotational bands built on
deformed cluster configurations predicted by antisymmetrized molecular dynamics
(AMD) calculations. The spin alignment mechanism is shown to be useful for
making spin assignments and may have widespread use.
