shifted momentum distribution in our work. A total cross section of 2.4(4) mb is indeed obtained by summing over the four states represented in red in Fig. 2. Contrary to the case presented in Ref. [22], the states here possibly produced by the same TS mechanism are below the neu-tron separation energy. This could be due to the fact that the neutron emission threshold of \( ^ { 3 5 } \mathrm { P } \) (\( S _ { n } \)=8.380 MeV) is much higher than the one of \( ^ { 3 5 } \mathrm { S i } \) (\( S _ { n } \)=2.470 MeV).

# VI. CONCLUSIONS

The spectroscopy of \( { } ^ { 3 5 } \mathbf { P } \) was investigated with an intermediate-energy one-proton knockout reaction using a secondary beam of \( ^ { 3 6 } \mathrm { S } \) interacting with a \( ^ { 9 } \mathrm { B e } \) foil at 88 MeV/u mid-target energy. The \( { } ^ { 3 5 } \mathbf { P } \) nuclei were selected by the S800 spectrograph at NSCL and identified in the spectrograph’s focal plane in coincidence with prompt \( \gamma \) rays detected in the GRETINA segmented Ge array around the target. The level scheme of \( { } ^ { 3 5 } \mathrm { P } \) has been es-tablished up to about 7.5 MeV from \( \gamma - \)\( \gamma \) coincidences and relative \( \gamma \) intensities. Spins and parities for most of the populated states were proposed from a comparison be-tween calculated and measured \( \gamma \)-gated momentum dis-tributions for the population of individual final states in \( { } ^ { 3 5 } \mathrm { P } \). Spectroscopic factor values, \( C ^ { 2 } S , \), were derived from partial cross sections for the \( 1 / 2 ^ { + } \) ground state and the excited states \( ( 3 / 2 ^ { + } \),\( 5 / 2 ^ { + } \) and tentatively \( 1 / 2 ^ { - } \)) in \( { } ^ { 3 5 } \mathrm { P } \). An inclusive cross section of 51(1) mb was measured for

\[ ^ { 3 5 } \mathbf { P } \]

produced from

\[ ^ { 3 6 } \mathrm { S } \]

. The extracted summed \( \sum C ^ { 2 } S \) values agree with expected shell-model occupancies of the protons in the \( 2 s _ { 1 / 2 } \) (\( \sum C ^ { 2 } S = \) 2.2(\( 7 ) \)), \( 1 d _ { 3 / 2 } \) (0.7(3)), \( 1 d _ { 5 / 2 } \) (5.2(9)) or-bitals, while only a fraction (0.41(17)) of the strength corresponding to the deeply-bound \( 1 p _ { 1 / 2 } \) orbit is tenta-tively observed for two states above 5.6 MeV.

The present results were compared to those obtained for \( { } ^ { 3 5 } \mathrm { \mathbf { P } } \) using the \( ^ { 3 6 } \mathrm { S } ( d , ^ { 3 } \mathrm { H e } ) { } ^ { 3 5 } \mathrm { P } \) transfer reaction at low energy. Remarkable agreement is found for the proposed level scheme populated, the spin assignments (except for one state) and the deduced \( C ^ { 2 } S \) values. Since ob-tained from high-resolution \( \gamma \)-ray spectroscopy, the ex-citation energies of the presently identified states in \( { } ^ { 3 5 } \mathrm { P } \) are more accurate than those obtained in the \( ( d , { ^ { 3 } \mathrm { H e } } ) \) reaction [16]. They agree with the values obtained in a multi-nucleon transfer reaction [25], for which several states were observed in common. The present sensitiv-ity of the knockout reaction, with a projectile beam of 2 \( \cdot \bar { 1 0 ^ { 5 } } \) pps, matches the one obtained in the \( ( d , { ^ 3 } \mathrm { H e } ) \) reac-tion with a d beam on a stable \( ^ { 3 6 } \mathrm { S } \) target. This reinforces the enormous potential of this experimental technique in extracting level schemes, orbital angular momenta, and \( C ^ { 2 } S \) values.

Besides the observation of states that were expected to be produced in the knockout of protons from the \( p - s d \) shell, other states with likely high spin value (\( J \ge 5 / \) 2) and negative parity are observed as well, with a summed partial cross section of about 2.4 mb. Owing to the facts that these states were not observed in the \( ( d , { ^ { 3 } \mathrm { H e } } ) \)) re-action and that they exhibit parallel-momentum distri-butions that are down-shifted as compared to the ones from knockout, we propose that they are produced by an-other mechanism that could be either a charge-exchange or a two-steps mechanism in which a core excitation is followed by a proton knockout. While so far we can-not clearly identify which of these two mechanisms is the most probable, it interestingly leads to the production of states most likely corresponding to neutron-core excita-tions. This feature may be very interesting to single-out intruder states belonging to the so-called island of inver-sion, as evoked in Refs. [22, 37].

# Acknowledgments

This work is supported by the National Science Foun-dation (NSF) under Grant Nos. PHY-1102511 and PHY-1306297 and by the Institut Universitaire de France. GRETINA was funded by the US DOE - Office of Sci-ence. Operation of the array at NSCL is supported by NSF under Cooperative Agreement PHY-1102511 (NSCL) and DOE under grant DE-AC02-05CH11231 (LBNL). O.S wish to thank T. Duguet for fruitful dis-cussions. J.A.T acknowledges support of the Science and Technology Facility Council (UK) grant ST/L005743.