We study low-lying states of even carbon isotopes in the range A = 10 - 20
within the large- scale no-core shell model (NCSM). Using several accurate
nucleon-nucleon (NN) as well as NN plus three-nucleon (NNN) interactions, we
calculate excitation energies of the lowest 2+ state, the electromagnetic B(E2;
2+1 -> 0+1) transition rates, the 2+1 quadrupole moments as well as se- lected
electromagnetic transitions among other states. Recent experimental campaigns
to measure 2+-state lifetimes indicate an interesting evolution of nuclear
structure that pose a challenge to reproduce theoretically from first
principles. Our calculations do not include any effective charges or other
fitting parameters. However, calculated results extrapolated to infinite model
spaces are also presented. The model-dependence of those results is discussed.
Overall, we find a good agree- ment with the experimentally observed trends,
although our extrapolated B(E2; 2+1 -> 0+1) value for 16C is lower compared to
the most recent measurements. Relative transition strengths from higher excited
states are investigated and the influence of NNN forces is discussed. In
particular for 16C we find a remarkable sensitivity of the transition rates
from higher excited states to the details of the nuclear interactions.Comment: 22 pages, 8 figures, preprint version. Accepted for publication in
Journal of Physics G: Nuclear and Particle Physic