The structure of the Hoyle state via a measurement of the 'Hoyle Rotational Band' in 12C

10th International Conference on Clustering Aspects of Nuclear Structure and Dynamics

Gai, M.^1,2

LNS at Avery Point, University of Connecticut, Groton, CT 06340-6097, United States^1

WNSL, Yale University, New Haven, CT 06520-8124, United States^2

关键词: Breathing modes;    Moment of inertia;    Optical time projection chamber;    Particle systems;    Relative phasis;    Rotation vibration;    Rotational band;    Triangular shapes;   

Others  :  https://iopscience.iop.org/article/10.1088/1742-6596/436/1/012007/pdf
DOI  :  10.1088/1742-6596/436/1/012007

来源: IOP

【 摘 要 】

We have measured the12C(γ, 3α) reaction with an Optical Time Projection Chamber (O-TPC) detector operating with the CO2(80%) + N2(20%) gas mixture and gamma-ray beams from the HIγS facility of the TUNL at Duke. We measured complete angular distributions (between 9.1 - 10.7 MeV) from which we determine the cross section yield curve and E1-E2 relative phases leading to an unambiguous identification of the second 2+state in12C at 10.03(11) MeV. The observed spectrum of12C below 12 MeV including the 22+observed in this work resembles the rotation-vibration spectrum predicted for a triangular shape oblate spinning top in which the Hoyle state is the first vibrational breathing mode of the triangular three alpha particle system. The predicted rotation-vibration spectrum of a triangular shape oblate spinning top (with a D3hsymmetry) allows us to compare the moment of inertia of the predicted Hoyle rotational band to the ground state rotational band and in this way extract the model radius parameter of the Hoyle state of 3.22(8) fm (√2 time the r.m.s. radius of the ground state) which is close to the radius extracted from12C(x,x′) data.