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Hyperfine spectra of $^\text{27-32}$Al ($Z=13$) have been measured at the ISOLDE-CERN facility via collinear laser spectroscopy using the $3s^23p\ ^2\text{P}^\text{o} _{3/2}\rightarrow 3s^24s\ ^2\text{S}_{1/2}$ atomic transition. For the first time, mean-square charge radii of radioactive aluminum isotopes have been determined alongside the previously unknown magnetic dipole moment of $^{29}$Al and electric quadrupole moments of $^{29,30}$Al. A potentially reduced charge radius at $N=19$ may suggest an effect of the $N=20$ shell closure, which is visible in the Al chain, contrary to other isotopic chains in the $sd$ shell. The experimental results are compared to theoretical calculations in the framework of the valence-space in-medium similarity renormalization group using multiple sets of two and three-nucleon forces from chiral effective field theory. While the trend of experimental magnetic dipole and electric quadrupole moments is well reproduced, the absolute values are underestimated by theory, consistent with earlier studies. Moreover, both the scale and trend of the charge radii appear to be very sensitive to the chosen interaction.

We present the first laser spectroscopic measurement of the neutron-rich nucleus ^{68}Ni at the N=40 subshell closure and extract its nuclear charge radius. Since this is the only short-lived isotope for which the dipole polarizability α_{D} has been measured, the combination of these observables provides a benchmark for nuclear structure theory. We compare them to novel coupled-cluster calculations based on different chiral two- and three-nucleon interactions, for which a strong correlation between the charge radius and dipole polarizability is observed, similar to the stable nucleus ^{48}Ca. Three-particle-three-hole correlations in coupled-cluster theory substantially improve the description of the experimental data, which allows to constrain the neutron radius and neutron skin of ^{68}Ni.

The one-loop contributions to the decays of the $CP$-odd and $CP$-even scalar bosons $A\to Z\gamma\gamma$ and $\phi\to Z\gamma\gamma$ ($\phi=h,H$) are calculated within the framework of $CP$-conserving THDMs, where they are induced by box and reducible Feynman diagrams. The behavior of the corresponding branching ratios are then analyzed within the type-II THDM in a region of the parameter space around the alignment limit and still consistent with experimental data. It is found that the $A\to Z\gamma\gamma$ branching ratio is only relevant when $m_A>m_H+m_Z$, but it is negligible otherwise. For $m_A>600$ GeV and $t_\beta\simeq O(1)$, $BR(A\to Z\gamma\gamma)$ can reach values of the order of $10^{-5}-10^{-4}$, but it decreases by about one order of magnitude as $t_\beta$ increases up to 10. A similar behavior is followed by the $H\to Z\gamma\gamma$ decay, which only has a non-negligible branching ratio when $m_H>m_A+m_Z$ and can reach the level of $10^{-4}-10^{-3}$ for $m_H>600$ GeV and $t_\beta\simeq O(1)$. We also estimated the branching ratios of these rare decays in the type-I THDM, where they can be about one order of magnitude larger than in type-II THDM. As far as the $h\to Z\gamma\gamma$ decay is concerned, since the properties of this scalar boson must be nearly identical to those of the SM Higgs boson, the $h\to Z\gamma\gamma$ branching ratio does not deviates significantly from the SM prediction, where it is negligibly small, of the order of $10^{-9}$. This result is in agreement with previous calculations.

The hyperfine spectra of $^{51,53-64}$Mn were measured in two experimental runs using collinear laser spectroscopy at ISOLDE, CERN. Laser spectroscopy was performed on the atomic $3d^5\ 4s^2\ ^{6}\text{S}_{5/2}\rightarrow 3d^5\ 4s4p\ ^{6}\text{P}_{3/2}$ and ionic $3d^5\ 4s\ ^{5}\text{S}_2 \rightarrow 3d^5\ 4p\ ^{5}\text{P}_3$ transitions, yielding two sets of isotope shifts. The mass and field shift factors for both transitions have been calculated in the multiconfiguration Dirac-Fock framework and were combined with a King plot analysis in order to obtain a consistent set of mean-square charge radii which, together with earlier work on neutron-deficient Mn, allow the study of nuclear structure changes from $N=25$ across $N=28$ up to $N=39$. A clear development of deformation is observed towards $N=40$, confirming the conclusions of the nuclear moments studies. From a Monte Carlo Shell Model study of the shape in the Mn isotopic chain, it is suggested that the observed development of deformation is not only due to an increase in static prolate deformation but also due to shape fluctuations and triaxiality. The changes in mean-square charge radii are well reproduced using the Duflo-Zuker formula except in the case of large deformation., Comment: 9 figures, submitted to PRC

Two different experiments observe nuclei with excited nuclear states that differ in shape from their ground states, so called shape coexistence. These nuclei lie close to the neutron-rich doubly-magic ${}^{78}$Ni region of the nuclear chart.

The ground-state spins and magnetic moments of $^{49,51}\mathrm{K}$ have been measured using bunched-beam high-resolution collinear laser spectroscopy at ISOLDE CERN. For $^{49}\mathrm{K}$ a ground-state spin $I=1/2$ was firmly established. The observed hyperfine structure of $^{51}\mathrm{K}$ requires a spin $Ig1/2$ and strongly suggests $I=3/2$. From its magnetic moment $\ensuremath{\mu}(^{51}\mathrm{K})=+0.5129(22){\ensuremath{\mu}}_{N}$ a spin-parity ${I}^{\ensuremath{\pi}}=3/{2}^{+}$ with a dominant $\ensuremath{\pi}1{d}_{3/2}^{\ensuremath{-}1}$ hole configuration was deduced. This establishes for the first time the reinversion of the single-particle levels and illustrates the prominent role of the residual monopole interaction for single-particle levels and shell evolution.

The nuclear charge radius of $^{12}\mathrm{Be}$ was precisely determined using the technique of collinear laser spectroscopy on the $2{s}_{1/2}\ensuremath{\rightarrow}2{p}_{1/2,3/2}$ transition in the ${\mathrm{Be}}^{+}$ ion. The mean square charge radius increases from $^{10}\mathrm{Be}$ to $^{12}\mathrm{Be}$ by $\ensuremath{\delta}⟨{r}_{c}^{2}{⟩}^{10,12}=0.69(5)\text{ }\text{ }{\mathrm{fm}}^{2}$ compared to $\ensuremath{\delta}⟨{r}_{c}^{2}{⟩}^{10,11}=0.49(5)\text{ }\text{ }{\mathrm{fm}}^{2}$ for the one-neutron halo isotope $^{11}\mathrm{Be}$. Calculations in the fermionic molecular dynamics approach show a strong sensitivity of the charge radius to the structure of $^{12}\mathrm{Be}$. The experimental charge radius is consistent with a breakdown of the $N=8$ shell closure.

Charge radii of all magnesium isotopes in the sd shell have been measured, revealing evolution of the nuclear shape throughout two prominent regions of assumed deformation centered on (24)Mg and (32)Mg. A striking correspondence is found between the nuclear charge radius and the neutron shell structure. The importance of cluster configurations towards N=8 and collectivity near N=20 is discussed in the framework of the fermionic molecular dynamics model. These essential results have been made possible by the first application of laser-induced nuclear orientation for isotope shift measurements.

Radio frequency spectra of a trapped unitary $^{6}\mathrm{Li}$ gas are reported and analyzed in terms of a theoretical approach that includes both final-state and trap effects. The different strength of the final-state interaction across the trap is crucial for evidencing two main peaks associated with two distinct phases residing in different trap regions. These are the pairing-gap and pseudo-gap phases below the critical temperature ${T}_{c}$, which evolve into the pseudo-gap and no-gap phases above ${T}_{c}$. In this way, a long standing puzzle about the interpretation of rf spectra for $^{6}\mathrm{Li}$ in a trap is solved.

Nuclear charge radii of ;{7,9,10,11}Be have been determined by high-precision laser spectroscopy. On-line measurements were performed with collinear laser spectroscopy in the 2s_{1/2}-->2p_{1/2} transition on a beam of Be+ ions. Collinear and anticollinear laser beams were used simultaneously, and the absolute frequency determination using a frequency comb yielded an accuracy in the isotope-shift measurements of about 1 MHz. Combining this with accurate calculations of the mass-dependent isotope shifts yields nuclear charge radii. The charge radius decreases from 7Be to 10Be and then increases for the halo nucleus 11Be. When comparing our results with predictions of ab initio nuclear-structure calculations we find good agreement. Additionally, the nuclear magnetic moment of 7Be was determined to be -1.3995(5)micro_{N} and that of 11Be was confirmed with an accuracy similar to previous beta-NMR measurements.

The nuclear charge radius of 11Li has been determined for the first time by high-precision laser spectroscopy. On-line measurements at TRIUMF-ISAC yielded a 7Li-11Li isotope shift (IS) of 25 101.23(13) MHz for the Doppler-free [FORMULA: SEE TEXT]transition. IS accuracy for all other bound Li isotopes was also improved. Differences from calculated mass-based IS yield values for change in charge radius along the isotope chain. The charge radius decreases monotonically from 6Li to 9Li, and then increases from 2.217(35) to 2.467(37) fm for 11Li. This is compared to various models, and it is found that a combination of halo neutron correlation and intrinsic core excitation best reproduces the experimental results.

Here we present the right way to extract interaction energies from dynamic measurements carried out for steps on $\mathrm{Si}(100)\ensuremath{-}2\ifmmode\times\else\texttimes\fi{}1;$ this remains as an unsolved problem. The determined interaction energies agree with those deduced via thermodynamic arguments from frozen patterns.

The superconducting transtition temperature ${T}_{c}$ in nonmagnetic ${\mathrm{Lu}}_{1\ensuremath{-}x}{\mathrm{La}}_{x}{\mathrm{Ni}}_{2}{\mathrm{B}}_{2}\mathrm{C}$ $(x\ensuremath{\leqslant}0.1)$ linearly decreases with the structural parameter ${c}^{\ensuremath{'}}∕a$ as $d{T}_{c}∕d({c}^{\ensuremath{'}}∕a)=210(20)\phantom{\rule{0.3em}{0ex}}\mathrm{K}$. The same decrease of $d{T}_{c}∕d({c}^{\ensuremath{'}}∕a)$ has been observed for the other nonmagnetic series ${\mathrm{Lu}}_{1\ensuremath{-}x}{\mathrm{Y}}_{x}{\mathrm{Ni}}_{2}{\mathrm{B}}_{2}\mathrm{C}$ $(x\ensuremath{\leqslant}0.1)$ [J. Freudenberger, S. L. Drechsler, G. Fuchs, A. Kreyssig, K. Nenkov, S. V. Shulga, K.-H. M\"uller, and L. Schultz, Physica C 306, 1 (1998); J. Freudenbenger, Paarbrechung in Seltenerd-\"Ubergangsmetall-Borkarbiden, Thesis, TU, Dresden, 2000]. The decrease in ${T}_{c}$ for the antiferromagnetically (AF) ordered compounds $\mathrm{R}{\mathrm{Ni}}_{2}{\mathrm{B}}_{2}\mathrm{C}$ ($R=\mathrm{Dy}$,Ho,Er,Tm) and for nonmagnetic LuNiBC again scales as $[d{T}_{c}∕d({c}^{\ensuremath{'}}∕a)]=200(10)\mathrm{K}$. This is a strong indication that in nonmagnetic and AF ordered $R{\mathrm{Ni}}_{2}{\mathrm{B}}_{2}\mathrm{C}$ as well as RNiBC compounds ${T}_{c}$ is determined by ${c}^{\ensuremath{'}}∕a$ which is a measure for the deviation of the $\mathrm{Ni}{\mathrm{B}}_{4}$ tetrahedra from ideal tetrahedral symmetry.

The homometallic $\mathrm{Fe}$ ludwigite ${\mathrm{Fe}}_{3}{\mathrm{O}}_{2}{\mathrm{BO}}_{3}$, is an oxyborate with a chain structure of oxygen octahedra occupied by ${\mathrm{Fe}}^{2+}$ and ${\mathrm{Fe}}^{3+}$ with four different crystallographic sites. We report $^{57}\mathrm{Fe}$ M\"ossbauer spectroscopic studies on the magnetic spin arrangements and on the charge ordering in ${\mathrm{Fe}}_{3}{\mathrm{O}}_{2}{\mathrm{BO}}_{3}$, between $4$ and $450\phantom{\rule{0.3em}{0ex}}\mathrm{K}$. From the temperature dependence of the isomer shifts and quadrupole interactions, together with the information from previous x-ray and transport data, we are able to discuss the structural arrangement of ${\mathrm{Fe}}^{2+}$ and ${\mathrm{Fe}}^{3+}$ and the dynamics of the electronic configurations. Below ${T}_{N1}=112\phantom{\rule{0.3em}{0ex}}\mathrm{K}$ the M\"ossbauer spectra show the onset of antiferromagnetic order only for a fraction of the $\mathrm{Fe}$ ions, the complementary fraction remaining paramagnetic down to $74\phantom{\rule{0.3em}{0ex}}\mathrm{K}$. Below $74\phantom{\rule{0.3em}{0ex}}\mathrm{K}$ all the sample becomes magnetically ordered, and an increase and a canting of the magnetic hyperfine field for each $\mathrm{Fe}$ ion is observed. This canting is related to the presence of weak ferromagnetism, as proposed from magnetization measurements. Below $\ensuremath{\sim}50\phantom{\rule{0.3em}{0ex}}\mathrm{K}$ antiferromagnetic order is found. From M\"ossbauer spectra taken under applied external magnetic fields, there is strong evidence for magnetic short-range order above ${T}_{N1}$ involving ferromagnetic clusters. The observed magnetic transitions appear to be clearly related to charge ordering.

The $2s\ensuremath{\rightarrow}3s$ transition of $^{6,7,8,9}\mathrm{L}\mathrm{i}$ was studied by high-resolution laser spectroscopy using two-photon Doppler-free excitation and resonance-ionization detection. Hyperfine structure splittings and isotope shifts were determined with precision at the 100 kHz level. Combined with recent theoretical work, the changes in the nuclear-charge radii of $^{8,9}\mathrm{L}\mathrm{i}$ were determined. These are now the lightest short-lived isotopes for which the charge radii have been measured. It is found that the charge radii monotonically decrease with increasing neutron number from $^{6}\mathrm{L}\mathrm{i}$ to $^{9}\mathrm{L}\mathrm{i}$.