The hyperfine coupling constants of neutron deficient 37 Ca were deduced from the atomic hyperfine spectrum of the 4s 2 S 1/2 ↔ 4p 2 P 3/2 transition in Ca II, measured using the collinear laser spectroscopy technique. The ground-state magnetic-dipole and spectroscopic electric-quadrupole moments were determined for the first time as µ = +0.7453(72)µN and Q = −15(11) e 2 fm 2 , respectively. The experimental values agree well with nuclear shell model calculations using the USDA/B interactions in the sd-model space with a 95% probability of the canonical nucleon configuration.It is shown that the magnetic moment of 39 Ca requires a larger non-sd-shell component than that of 37 Ca for good agreement with the shell-model calculation, indicating a more robust closed subshell structure of 36 Ca at the neutron number N = 16 than 40 Ca. The results are also compared to valence-space in-medium similarity renormalization group calculations based on chiral two-and three-nucleon interactions.
Mating displays often contain multiple signals. Different combinations of these signals may be equally successful at attracting a mate, as environment and signal combination may influence relative signal weighting by choosy individuals. This variation in signal weighting among choosy individuals may facilitate the maintenance of polymorphic displays and signalling behaviour. One group of animals known for their polymorphic patterning are Batesian mimetic butterflies, where the interaction of sexual selection and predation pressures is hypothesized to influence the maintenance of polymorphic wing patterning and behaviour. Males in the female‐limited polymorphic Batesian mimetic butterfly Papilio polytes use female wing pattern and female activity levels when determining whom to court. They court stationary females with mimetic wing patterns more often than stationary females with non‐mimetic, male‐like wing patterns and active females more often than inactive females. It is unclear whether females modify their behaviour to increase (or decrease) their likelihood of receiving male courtship, or whether non‐mimetic females spend more time in cryptic environments than mimetic females, to compensate for their lack of mimicry‐driven predation protection (at the cost of decreased visibility to males). In addition, relative signal weighting of female wing pattern and activity to male mate selection is unknown. To address these questions, we conducted a series of observational studies of a polymorphic P. polytes population in a large butterfly enclosure. We found that males exclusively courted active females, irrespective of female wing pattern. However, males did court active non‐mimetic females significantly more often than expected given their relative abundance in the population. Females exhibited similar activity levels, and selected similar resting environments, irrespective of wing pattern. Our results suggest that male preference for non‐mimetic females may play an active role in the maintenance of the non‐mimetic female form in natural populations, where males are likely to be in the presence of active, as well as inactive, mimetic and non‐mimetic females.
Nuclear charge radii of 55;56 Ni were measured by collinear laser spectroscopy. The obtained information completes the behavior of the charge radii at the shell closure of the doubly magic nucleus 56 Ni. The trend of charge radii across the shell closures in calcium and nickel is surprisingly similar despite the fact that the 56 Ni core is supposed to be much softer than the 48 Ca core. The very low magnetic moment μð 55 NiÞ ¼ −1.108ð20Þ μ N indicates the impact of M1 excitations between spin-orbit partners across the N; Z ¼ 28 shell gaps. Our charge-radii results are compared to ab initio and nuclear density functional theory calculations, showing good agreement within theoretical uncertainties.
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