Search

Background: Mainly because of its long half-life and despite its scientific relevance, spectroscopic measurements of Lu176 forbidden β decays are very limited and lack formulation of shape factors. A direct precise measurement of its Q value is also presently unreported. In addition, the description of forbidden decays provides interesting challenges for nuclear theory. The comparison of precise experimental results with theoretical calculations for these decays can help to test underlying models and can aid the interpretation of data from other experiments. Purpose: Perform the first precision measurements of Lu176β-decay spectra and attempt the observation of its electron capture decays, as well as perform the first precision direct measurement of the Lu176β-decay Q value. Compare the shape of the precisely determined experimental β spectra to theoretical calculations, and compare the end point energy to that obtained from an independent Q value measurement. Method: The Lu176β-decay spectra measurements and the search for electron capture decays were performed with an experimental setup that employed lutetium-containing scintillator crystals and a NaI(Tl) spectrometer for coincidence counting. The β decay Q value was determined via high-precision Penning trap mass spectrometry (PTMS) with the LEBIT facility at the National Superconducting Cyclotron Laboratory. The β-spectrum calculations were performed within the Fermi theory formalism with nuclear structure effects calculated using a shell model approach. Results: Both β transitions of Lu176 were experimentally observed and corresponding shape factors formulated in their entire energy ranges. The search for electron capture decay branches led to an experimental upper limit of 6.3×10-6 relative to its β decays. The Lu176β-decay and electron capture Q values were measured using PTMS to be 1193.0(6) and 108.9(8) keV, respectively. This enabled precise β end point energies of 596.2(6) and 195.3(6) keV to be determined for the primary and secondary β decays, respectively. The conserved vector current hypothesis was applied to calculate the relativistic vector matrix elements. The β-spectrum shape was shown to significantly depend on the Coulomb displacement energy and on the value of the axial vector coupling constant gA, which was extracted according to different assumptions. Conclusion: The implemented self-scintillation method has provided unmatched observations of Lu176, independently validated by the first direct measurements of its β-decay Q value by Penning trap mass spectrometry. Theoretical study of the main β transition led to the extraction of very different effective gA and log10f values, showing that a high-precision description of this transition would require a realistic nuclear structure with nucleus deformation.

We performed a Penning trap mass measurement of $^{61}{\rm Zn}$ at the National Superconducting Cyclotron Laboratory and NuShellX calculations of the $^{61}{\rm Zn}$ and $^{62}{\rm Ga}$ structure using the GXPF1A Hamiltonian to obtain improved estimates of the $^{61}{\rm Zn}(p,\gamma)^{62}{\rm Ga}$ and $^{60}{\rm Cu}(p,\gamma)^{61}{\rm Zn}$ reaction rates. Surveying astrophysical conditions for type-I X-ray bursts with the code MESA, implementing our improved reaction rates, and taking into account updated nuclear masses for $^{61}{\rm V}$ and $^{61}{\rm Cr}$ from the recent literature, we refine the neutrino luminosity from the important mass number $A=61$ urca cooling source in accreted neutron star crusts. This improves our understanding of the thermal barrier between deep heating in the crust and the shallow depths where extra heat is needed to explain X-ray superbursts, as well as the expected signature of crust urca neutrino emission in light curves of cooling transients., Comment: Submitted

Background: The quadratic isobaric multiplet mass equation (IMME) has been very successful at predicting the masses of isobaric analog states in the same multiplet, while its coefficients are known to follow specific trends as functions of mass number. The Atomic Mass Evaluation 2016 [Chin. Phys. C 41, 030003 (2017)] $^{44}\mathrm{V}$ mass value results in an anomalous negative $c$ coefficient for the IMME quadratic term; a consequence of large uncertainty and an unresolved isomeric state. The $b$ and $c$ coefficients can provide useful constraints for construction of the isospin-nonconserving Hamiltonians for the $pf$ shell. In addition, the excitation energy of the ${0}^{+},T=2$ level in $^{44}\mathrm{V}$ is currently unknown. This state can be used to constrain the mass of the more exotic $^{44}\mathrm{Cr}$.Purpose: The aim of the experimental campaign was to perform high-precision mass measurements to resolve the difference between $^{44}\mathrm{V}$ isomeric and ground states, to test the IMME using the new ground state mass value and to provide necessary ingredients for the future identification of the ${0}^{+}$, $T=2$ state in $^{44}\mathrm{V}$.Method: High-precision Penning trap mass spectrometry was performed at LEBIT, located at the National Superconducting Cyclotron Laboratory, to measure the cyclotron frequency ratios of [${^{44g,m}\mathrm{VO}]}^{+}$ versus [${^{32}\mathrm{SCO}]}^{+}$, a well-known reference mass, to extract both the isomeric and ground state masses of $^{44}\mathrm{V}$.Results: The mass excess of the ground and isomeric states in $^{44}\mathrm{V}$ were measured to be $\ensuremath{-}23\phantom{\rule{4pt}{0ex}}804.9(80)$ keV/${c}^{2}$ and $\ensuremath{-}23\phantom{\rule{4pt}{0ex}}537.0(55)$ keV/${c}^{2}$, respectively. This yielded a new proton separation energy of ${S}_{p}=1\phantom{\rule{4pt}{0ex}}773(10)$ keV.Conclusion: The new values of the ground state and isomeric state masses of $^{44}\mathrm{V}$ have been used to deduce the IMME $b$ and $c$ coefficients of the lowest ${2}^{+}$ and ${6}^{+}$ triplets in $A=44$. The ${2}^{+}\phantom{\rule{4pt}{0ex}}c$ coefficient is now verified with the IMME trend for lowest multiplets and is in good agreement with the shell-model predictions using charge-dependent Hamiltonians. The mirror energy differences were determined between $^{44}\mathrm{V}$ and $^{44}\mathrm{Sc}$, in line with isospin-symmetry for this multiplet. The new value of the proton separation energy determined, to an uncertainty of 10 keV, will be important for the determination of the ${0}^{+}$, $T=2$ state in $^{44}\mathrm{V}$ and, consequently, for prediction of the mass excess of $^{44}\mathrm{Cr}$.

Background: The understanding and description of forbidden decays provides interesting challenges for nuclear theory. These calculations could help to test underlying nuclear models and interpret experimental data.Purpose: Compare a direct measurement of the $^{138}\mathrm{La}\phantom{\rule{4pt}{0ex}}\ensuremath{\beta}$-decay $Q$ value with the $\ensuremath{\beta}$-decay spectrum end-point energy measured by Quarati et al. using ${\mathrm{LaBr}}_{3}$ detectors [Appl. Radiat. Isot. 108, 30 (2016)]. Use new precise measurements of the $^{138}\mathrm{La}\phantom{\rule{4pt}{0ex}}\ensuremath{\beta}$-decay and electron capture (EC) $Q$ values to improve theoretical calculations of the $\ensuremath{\beta}$-decay spectrum and EC probabilities.Method: High-precision Penning trap mass spectrometry was used to measure cyclotron frequency ratios of $^{138}\mathrm{La}$, $^{138}\mathrm{Ce}$, and $^{138}\mathrm{Ba}$ ions from which $\ensuremath{\beta}$-decay and EC $Q$ values for $^{138}\mathrm{La}$ were obtained.Results: The $^{138}\mathrm{La}\phantom{\rule{4pt}{0ex}}\ensuremath{\beta}$-decay and EC $Q$ values were measured to be ${Q}_{\ensuremath{\beta}}=1052.42(41)$ keV and ${Q}_{\mathrm{EC}}=1748.41(34)$ keV, improving the precision compared to the values obtained in the most recent atomic mass evaluation [Wang et al., Chin. Phys. C 41, 030003 (2017)] by an order of magnitude. These results are used for improved calculations of the $^{138}\mathrm{La}\phantom{\rule{4pt}{0ex}}\ensuremath{\beta}$-decay shape factor and EC probabilities. New determinations for the $^{138}\mathrm{Ce}$ 2EC $Q$ value and the atomic masses of $^{138}\mathrm{La}$, $^{138}\mathrm{Ce}$, and $^{138}\mathrm{Ba}$ are also reported.Conclusion: The $^{138}\mathrm{La}\phantom{\rule{4pt}{0ex}}\ensuremath{\beta}$-decay $Q$ value measured by Quarati et al. is in excellent agreement with our new result, which is an order of magnitude more precise. Uncertainties in the shape factor calculations for $^{138}\mathrm{La}\phantom{\rule{4pt}{0ex}}\ensuremath{\beta}$ decay using our new $Q$ value are reduced by an order of magnitude. Uncertainties in the EC probability ratios are also reduced and show improved agreement with experimental data.

A laser ablation ion source has been developed and implemented at the Low-Energy Beam and Ion Trap (LEBIT) facility at the National Superconducting Cyclotron Laboratory. This offline ion source enhances the capabilities of LEBIT by providing increased access to ions used for calibration measurements and checks of systematic effects as well as stable and long-lived ions of scientific interest. The design of the laser ablation ion source and a demonstration of its successful operation are presented.

Background: The $^{51}\mathrm{Fe}(p,\ensuremath{\gamma})^{52}\mathrm{Co}$ reaction lies along the main rp-process path leading up to the $^{56}\mathrm{Ni}$ waiting point. The uncertainty in the reaction $Q$ value, which determines the equilibrium between the forward proton-capture and reverse photodisintegration $^{52}\mathrm{Co}(\ensuremath{\gamma},p)^{51}\mathrm{Fe}$ reaction, contributes to considerable uncertainty in the reaction rate in the temperature range of interest for Type I x-ray bursts and thus to an $\ensuremath{\approx}10%$ uncertainty in burst ashes lighter than $A=56$.Purpose: With a recent Penning trap mass measurement of $^{52}\mathrm{Co}$ reducing the uncertainty on its mass to 6.6 keV [Nesterenko et al., J. Phys. G 44, 065103 (2017)], the dominant source of uncertainty in the reaction $Q$ value is now the mass of $^{51}\mathrm{Fe}$, reported in the 2016 atomic mass evaluation to a precision of 9 keV [Wang et al., Chin. Phys. C 41, 030003 (2017)]. A new, high-precision Penning trap mass measurement of $^{51}\mathrm{Fe}$ was performed to allow the determination of an improved precision $Q$ value and thus new reaction rates.Method: $^{51}\mathrm{Fe}$ was produced using projectile fragmentation at the Coupled Cyclotron Facility at the National Superconducting Cyclotron Laboratory, and separated using the A1900 fragment separator. The resulting secondary beam was then thermalized in the beam stopping area before a mass measurement was performed using the LEBIT 9.4T Penning trap mass spectrometer.Results: The new mass excess, $\mathrm{ME}=\ensuremath{-}40189.2(1.6)$ keV, is sixfold more precise than the current AME value, and $1.6\ensuremath{\sigma}$ less negative. This value was used to calculate a new proton separation energy for $^{52}\mathrm{Co}$ of 1431(7) keV. New excitation levels were then calculated for $^{52}\mathrm{Co}$ using the nushellx code with the GXPF1A interaction, and a new reaction rate and burst ash composition was calculated.Conclusions: With a new measured $Q$ value, the uncertainty on the $^{51}\mathrm{Fe}(p,\ensuremath{\gamma})$ reaction rate is dominated by the poorly measured $^{52}\mathrm{Co}$ level structure. Reducing this uncertainty would allow a more precise rate calculation and a better determination of the mass abundances in the burst ashes.

International audience; We discuss the motivation and technique of Penning trap mass spectrometry applied to radioactive$^{44}$V and$^{44}^{m}$V, using the LEBIT 9.4 T Penning trap mass spectrometer at the National Superconducting Cyclotron Laboratory (NSCL) at Michigan State University. A complementary measurement of these nuclides, performed at the CSRe in Lanzhou, China, was recently published, but with errors several times larger than obtainable for a short-lived radionuclide in a Penning trap. Interpretation of the higher precision results is ongoing and a full accounting of this measurement is anticipated in the coming months.

We report the mass measurement of $^{56}\mathrm{Cu}$, using the LEBIT 9.4 T Penning trap mass spectrometer at the National Superconducting Cyclotron Laboratory at Michigan State University. The mass of $^{56}\mathrm{Cu}$ is critical for constraining the reaction rates of the $^{55}\mathrm{Ni}(p,\ensuremath{\gamma})$ $^{56}\mathrm{Cu}(p,\ensuremath{\gamma})$ $^{57}\mathrm{Zn}({\ensuremath{\beta}}^{+})$ $^{57}\mathrm{Cu}$ bypass around the $^{56}\mathrm{Ni}$ waiting point. Previous recommended mass excess values have disagreed by several hundred keV. Our new value, $\mathrm{ME}=\ensuremath{-}38626.7(7.1)\text{ }\text{ }\mathrm{keV}$, is a factor of 30 more precise than the extrapolated value suggested in the 2012 atomic mass evaluation [Chin. Phys. C 36, 1603 (2012)], and more than a factor of 12 more precise than values calculated using local mass extrapolations, while agreeing with the newest 2016 atomic mass evaluation value [Chin. Phys. C 41, 030003 (2017)]. The new experimental average, using our new mass and the value from AME2016, is used to calculate the astrophysical $^{55}\mathrm{Ni}(p,\ensuremath{\gamma})$ and $^{56}\mathrm{Cu}(p,\ensuremath{\gamma})$ forward and reverse rates and perform reaction network calculations of the $rp$ process. These show that the $rp$-process flow redirects around the $^{56}\mathrm{Ni}$ waiting point through the $^{55}\mathrm{Ni}(p,\ensuremath{\gamma})$ route, allowing it to proceed to higher masses more quickly and resulting in a reduction in ashes around this waiting point and an enhancement to higher-mass ashes.

The region near Z=28, N=40 is a subject of great interest for nuclear structure studies due to spectroscopic signatures in $^{68}$Ni suggesting a subshell closure at N=40. Trends in nuclear masses and their derivatives provide a complementary approach to shell structure investigations via separation energies. Penning trap mass spectrometry has provided precise measurements for a number of nuclei in this region, however a complete picture of the mass surfaces has so far been limited by the large uncertainty remaining for nuclei with N > 40 along the iron and cobalt chains. Here we present the first Penning trap measurements of $^{68,69}$Co, performed at the Low-Energy Beam and Ion Trap facility at the National Superconducting Cyclotron Laboratory. In addition, we perform ab initio calculations of ground state and two-neutron separation energies of cobalt isotopes with the valence-space in-medium similarity renormalization group approach based on a particular set of two- and three-nucleon forces which predict saturation in infinite matter. We discuss the importance of these measurements and calculations for understanding the evolution of nuclear structure near $^{68}$Ni., 7 pages, 6 figures

Using high-precision Penning trap mass spectrometry at the Low Energy Beam and Ion Trap facility at the National Superconducting Cyclotron Laboratory we have measured the $Q$ values of the fourth-order forbidden $\ensuremath{\beta}$ decay and electron capture of $^{50}\mathrm{V}$ and the double electron capture $Q$ value of $^{50}\mathrm{Cr}$ with the results ${Q}_{\ensuremath{\beta}}(^{50}\mathrm{V})=1038.1(1)$ keV, ${Q}_{\mathrm{EC}}(^{50}\mathrm{V})=2208.7(1)$ keV, and ${Q}_{2\mathrm{EC}}(^{50}\mathrm{Cr})=1170.5(1)$ keV. In addition, we have measured the atomic masses of $^{46,47,49,50}\mathrm{Ti},^{50,51}\mathrm{V}$, and $^{50,52--54}\mathrm{Cr}$, reducing uncertainties by factors of up to three compared with the most recent atomic mass evaluation $(Ame2016)$ [Chin. Phys. C 41, 030003 (2017)]. Our results are in good agreement with $Ame2016$ for $^{46,47,49,50}\mathrm{Ti}$ and $^{50,54}\mathrm{Cr}$ and show deviations of up to $\ensuremath{\sim}1\phantom{\rule{4pt}{0ex}}\mathrm{keV}\phantom{\rule{4pt}{0ex}}(2.5\ensuremath{\sigma})$ for $^{50,51}\mathrm{V}$ and $^{50,54}\mathrm{Cr}$.

We report the mass measurement of ^{56}Cu, using the LEBIT 9.4 T Penning trap mass spectrometer at the National Superconducting Cyclotron Laboratory at Michigan State University. The mass of ^{56}Cu is critical for constraining the reaction rates of the ^{55}Ni(p,γ) ^{56}Cu(p,γ) ^{57}Zn(β^{+}) ^{57}Cu bypass around the ^{56}Ni waiting point. Previous recommended mass excess values have disagreed by several hundred keV. Our new value, ME=-38626.7(7.1) keV, is a factor of 30 more precise than the extrapolated value suggested in the 2012 atomic mass evaluation [Chin. Phys. C 36, 1603 (2012)CPCHCQ1674-113710.1088/1674-1137/36/12/003], and more than a factor of 12 more precise than values calculated using local mass extrapolations, while agreeing with the newest 2016 atomic mass evaluation value [Chin. Phys. C 41, 030003 (2017)CPCHCQ1674-113710.1088/1674-1137/41/3/030003]. The new experimental average, using our new mass and the value from AME2016, is used to calculate the astrophysical ^{55}Ni(p,γ) and ^{56}Cu(p,γ) forward and reverse rates and perform reaction network calculations of the rp process. These show that the rp-process flow redirects around the ^{56}Ni waiting point through the ^{55}Ni(p,γ) route, allowing it to proceed to higher masses more quickly and resulting in a reduction in ashes around this waiting point and an enhancement to higher-mass ashes.

The goal of this paper was to investigate gas-phase structures of conformers of doubly charged phosphopeptide ions (ApSAAR + 2H) 2+ and (AApSAR + 2H) 2+ using traveling-wave and drift-tube ion mobility and IR action spectroscopy measurements in combination with molecular dynamics and electronic structure calculations. Lowest free-energy conformers were identified by extensive search of the conformational space with combined molecular dynamics, semi-empirical, density functional theory and perturbational Moller–Plesset ab initio calculations. The low-energy conformers had collisional cross sections that were compatible with the experimental data but did not allow the conformers to be distinguished. IR absorption spectra that were calculated by density functional theory for harmonic normal modes showed several intense bands that were absent in the experimental action spectrum. Agreement with experiment was improved upon implementing second-order anharmonic corrections to the calculated vibrational frequencies. Several factors affecting the action spectra are discussed such as effects of mode anharmonicity on the absorption band intensities, the magnitude of frequency shifts in anharmonic corrections, as well as non-linear effects in multiple-photon absorption that may suppress the detection of strongly H-bonded modes in these measurements.

A gas-phase radical rearrangement through intramolecular hydrogen-atom transfer (HAT) was studied in the glutathione radical cation, [-ECG](+.), which was generated by a homolytic cleavage of the protonated S-nitrosoglutathione. Ion-molecule reactions suggested that the radical migrates from the original sulfur position to one of the -carbon atoms. Experiments on the radical cations of dipeptides derived from the glutathione sequence, [-EC](+.) and [CG](+.), pointed to the glutamic acid -carbon atom as the most likely site of the radical migration. Infrared multiple-photon dissociation (IRMPD) spectroscopy was employed to generate complementary information. IRMPD of [-ECG](+.) in the approximately 1000-1800cm(-1) region was inconclusive owing to the relatively broad, overlapping absorption bands. However, the IRMPD spectrum of [-EC](+.) in this region was consistent with the radical migrating from the sulfur to the -carbon atom of glutamic acid. IRMPD in the 2800-3700cm(-1) region performed on [-ECG](+.) is consistent with a mixture of both the original sulfur-based radical and the resulting glutamic acid -carbon-based species. Comparisons are made with previously published condensed and gas-phase studies on intramolecular HAT in glutathione.

Background: The observation of neutrinoless double-$\ensuremath{\beta}$ transitions would indicate physics beyond the standard model as the lepton number conservation is violated. For a complete degeneracy in the energy of the initial and final states, the neutrinoless double-electron capture is resonantly enhanced. This shortens the half-life to similar orders of magnitude as the neutrinoless double-$\ensuremath{\beta}$ decay and expands the set of nuclei for the search of neutrinoless double-$\ensuremath{\beta}$ transitions as the observation of either process would be equally likely.Purpose: To clearly identify transitions that are resonantly enhanced, among other parameters the total energy of the decay, ${Q}_{\ensuremath{\varepsilon}\ensuremath{\varepsilon}}$, needs to be measured very precisely. Of the 12 initially identified candidates, the last remaining decay without a precise ${Q}_{\ensuremath{\varepsilon}\ensuremath{\varepsilon}}$ was $^{190}\mathrm{Pt}(0\ensuremath{\nu}\ensuremath{\varepsilon}\ensuremath{\varepsilon})^{190}\mathrm{Os}$.Method: The ${Q}_{\ensuremath{\varepsilon}\ensuremath{\varepsilon}}$ value was determined with the Penning trap mass spectrometer LEBIT by measuring the ratio of the cyclotron frequencies of $^{190}\mathrm{Pt}^{+}$ and $^{190}\mathrm{Os}^{+}$ in a 9.4-T superconducting magnet.Result: The ${Q}_{\ensuremath{\varepsilon}\ensuremath{\varepsilon}}$ value was determined to be 1401.57(47) keV with an uncertainty reduction of an order of magnitude compared to its previously known value. The absolute value is shifted by 17.17(623) keV relative to the previously accepted one. Furthermore, the mass value of $^{190}\mathrm{Pt}$ was found to be shifted by more than three standard deviations. In addition we improved the mass values for $^{186,190}\mathrm{Os}$ and $^{194}\mathrm{Pt}$.Conclusion: Transitions to the two nuclear excited states of $^{190}\mathrm{Os}$ with 1326.9(5) and 1387.00(2) keV energy were identified to be resonantly enhanced within a $1\ensuremath{\sigma}$ uncertainty. The significantly reduced uncertainty of ${Q}_{\ensuremath{\varepsilon}\ensuremath{\varepsilon}}$ confirmed the potential for a resonantly enhanced transition.

We present an infrared laser-based mass spectrometric strategy to differentiate peptides that are phosphorylated (i.e., containing pS, pT, or pY) from those that are nonphosphorylated (i.e., containing S, T, or Y), and those peptides that have none of these moieties (i.e., containing neither pS, pT, pY nor S, T, Y). This is demonstrated for a series of tripeptides and for two larger octapeptides, showing that the diagnostic phosphate OH stretch (indicative for pS, pT, or pY) can be distinguished from the alcohol OH stretch (indicative for S, T, or Y). In addition, the infrared multiple photon dissociation (IRMPD) spectra of multiple peptide analytes are recorded simultaneously in a multiplexed fashion. This is achieved by complexing each peptide precursor with a noncovalently bound 18-crown-6 ether, which is detached upon resonant infrared photon absorption.

We report infrared multiple photon dissociation (IRMPD) spectra for a series of crown-adducted, protonated amino acids, generated by electrospray ionization. The tight chelation of 18-crown-6 on the protonated NH(3)(+) moiety results in a considerable red shift of the NH(3)(+) stretch modes, notably the antisymmetric NH(3)(+) stretch. This is rationalized by a distortion of the NH(3)(+) normal mode potential energy surface, as verified by quantum chemical calculations. On the other hand, the local oscillator modes, such as the carboxylic acid OH stretch, indole NH stretch, and phenol OH stretches, remain well-resolved and are subject to minor and predictable blue shifts of 5-15 cm(-1). Other chemically diagnostic modes, such as the guanidine NH stretch and alcohol OH stretches, also have discernible band positions. Crucially, some of these diagnostic band positions have little to no overlap with one another and can hence be readily distinguished. In addition, the complexes are often found to efficiently photodissociate by neutral loss of 18-crown-6, particularly for higher-basicity amino acids. This in principle opens the door on multiplexing the IRMPD experiment, where the IR spectra of multiple precursors are recorded simultaneously.

We report infrared multiple-photon dissociation (IRMPD) spectra of protonated tryptophan, TrpH+, as well as the dissociation products from NH3 loss, [Trp+H−NH3]+, and subsequent CH2CO loss, [Trp+H−NH3−CH2CO]+. These results were obtained using a custom-built mass spectrometer, where the mass-isolated ions were photodissociated by a tunable optical parametric oscillator laser in a reduced-pressure (i.e., 10−5 mbar) “Paul-type” 3D ion trap. A comparison to computed spectra of putative conformations for TrpH+ shows that the protonated amino group, NH3+, interacts with the carboxylic acid carbonyl oxygen and the aromatic indole side chain. Ammonia loss is confirmed to occur via nucleophilic attack from C3 on the indole side chain, as opposed to C2 or C4, resulting in a spirocyclopropane structure with the charge located on the indole side chain. For the consecutive [Trp+H−NH3−CH2CO]+ product, the agreement with theory is slightly less persuasive, even if the qualitative trends are in accordance with the propo...

We report the determination of the Q(EC) value of the mirror transition of (11)C by measuring the atomic masses of (11)C and (11)B using Penning trap mass spectrometry. More than an order of magnitude improvement in precision is achieved as compared to the 2012 Atomic Mass Evaluation (Ame2012) [Chin. Phys. C 36, 1603 (2012)]. This leads to a factor of 3 improvement in the calculated Ft value. Using the new value, Q(EC)=1981.690(61) keV, the uncertainty on Ft is no longer dominated by the uncertainty on the Q(EC) value. Based on this measurement, we provide an updated estimate of the Gamow-Teller to Fermi mixing ratio and standard model values of the correlation coefficients.

The study of the nuclear polarization of radon is motivated by the expected large enhancement of sensitivity to a CP-violating electric dipole moment (EDM) in isotopes with octupole deformation or vibrational strength. In preparation for EDM measurements, the polarization of radon by spin exchange with laser-polarized alkali metals is studied. The measurement of the alignment of 209Rn using HPGe detectors to observe the resulting anisotropy in the 337 and 745 keV gamma rays emitted following electron-capture decay of 209Rn to 209At is demonstrated. Radon is polarized via spin-exchange collisions with rubidium atoms in an uncoated Pyrex optical pumping cell. Anisotropy measurements at several temperatures are used to study polarization and relaxation.

We report the determination of the Q(EC) value of the mirror transition of (11)C by measuring the atomic masses of (11)C and (11)B using Penning trap mass spectrometry. More than an order of magnitude improvement in precision is achieved as compared to the 2012 Atomic Mass Evaluation (Ame2012) [Chin. Phys. C 36, 1603 (2012)]. This leads to a factor of 3 improvement in the calculated Ft value. Using the new value, Q(EC)=1981.690(61) keV, the uncertainty on Ft is no longer dominated by the uncertainty on the Q(EC) value. Based on this measurement, we provide an updated estimate of the Gamow-Teller to Fermi mixing ratio and standard model values of the correlation coefficients.

We report the first direct measurement of the $^{14}\mathrm{O}$ superallowed Fermi $\ensuremath{\beta}$-decay ${Q}_{EC}$ value, the last of the so-called ``traditional nine'' superallowed Fermi $\ensuremath{\beta}$ decays to be measured with Penning trap mass spectrometry. $^{14}\mathrm{O}$, along with the other low-$Z$ superallowed $\ensuremath{\beta}$ emitter, $^{10}\mathrm{C}$, is crucial for setting limits on the existence of possible scalar currents. The new ground state ${Q}_{EC}$ value, 5144.364(25) keV, when combined with the energy of the ${0}^{+}$ daughter state, ${E}_{x}({0}^{+})=2312.798(11)\text{ }\text{ }\mathrm{keV}$ [, Nucl. Phys. A523, 1 (1991)], provides a new determination of the superallowed $\ensuremath{\beta}$-decay ${Q}_{EC}$ value, ${Q}_{EC}(\mathrm{sa})=2831.566(28)\text{ }\text{ }\mathrm{keV}$, with an order of magnitude improvement in precision, and a similar improvement to the calculated statistical rate function $f$. This is used to calculate an improved $\mathcal{F}t$ value of 3073.8(2.8) s.

Experimental searches for neutrinoless double-$\ensuremath{\beta}$ decay offer one of the best opportunities to look for physics beyond the standard model. Detecting this decay would confirm the Majorana nature of the neutrino, and a measurement of its half-life can be used to determine the absolute neutrino mass scale. Important to both tasks is an accurate knowledge of the $Q$ value of the double-$\ensuremath{\beta}$ decay. The LEBIT Penning trap mass spectrometer was used for the first direct experimental determination of the $^{96}\mathrm{Zr}$ double-$\ensuremath{\beta}$ decay $Q$ value: ${Q}_{\ensuremath{\beta}\ensuremath{\beta}}=3355.85(15)$ keV. This value is nearly 7 keV larger than the 2012 Atomic Mass Evaluation [M. Wang et al., Chin. Phys. C 36, 1603 (2012)] value and one order of magnitude more precise. The 3-$\ensuremath{\sigma}$ shift is primarily due to a more accurate measurement of the $^{96}\mathrm{Zr}$ atomic mass: $m{(}^{96}\mathrm{Zr})=95.908\phantom{\rule{0.16em}{0ex}}277\phantom{\rule{0.16em}{0ex}}35(17)$ u. Using the new $Q$ value, the $2\ensuremath{\nu}\ensuremath{\beta}\ensuremath{\beta}$-decay matrix element, $|{M}_{2\ensuremath{\nu}}|$, is calculated. Improved determinations of the atomic masses of all other zirconium $(^{90\ensuremath{-}92,94,96}\mathrm{Zr})$ and molybdenum $({}^{92,94\ensuremath{-}98,100}\mathrm{Mo})$ isotopes using both ${}^{12}{\mathrm{C}}_{8}$ and $^{87}\mathrm{Rb}$ as references are also reported.

We report the first direct measurement of the (14)O superallowed Fermi β-decay QEC value, the last of the so-called "traditional nine" superallowed Fermi β decays to be measured with Penning trap mass spectrometry. (14)O, along with the other low-Z superallowed β emitter, (10)C, is crucial for setting limits on the existence of possible scalar currents. The new ground state QEC value, 5144.364(25) keV, when combined with the energy of the 0(+) daughter state, Ex(0(+))=2312.798(11) keV [F. Ajzenberg-Selove, Nucl. Phys. A523, 1 (1991)], provides a new determination of the superallowed β-decay QEC value, QEC(sa)=2831.566(28) keV, with an order of magnitude improvement in precision, and a similar improvement to the calculated statistical rate function f. This is used to calculate an improved Ft value of 3073.8(2.8) s.

The Low Energy Beam and Ion Trap (LEBIT) Penning trap mass spectrometer was used to perform an improved-precision mass measurement of $^{72}\mathrm{Br}$ and the low-lying isomeric state, $^{72m}\mathrm{Br},$ giving mass excesses of $\ensuremath{-}59\phantom{\rule{0.16em}{0ex}}062.2(1.0)\phantom{\rule{0.16em}{0ex}}\mathrm{keV}$ and $\ensuremath{-}58\phantom{\rule{0.16em}{0ex}}960.9(1.2)\phantom{\rule{0.16em}{0ex}}\mathrm{keV}$, respectively. These values are consistent with the values from the 2012 atomic mass evaluation [Chin. Phys. C 36, 1603 (2012)] and the Nubase2012 evaluation of nuclear properties [Chin. Phys. C 36, 1157 (2012)]. The uncertainties on the mass of the ground state and isomeric state have been reduced by a factor of seven.

The radioactive element francium is of great interest in many laboratories because, as an alkali, it is the heaviest atom in which the atomic properties can presently be calculated to better than 1%. The electron-nucleus interactions in heavy atoms are stronger than in lighter alkalis and are more sensitive to weak interaction effects in nuclei, such as anapole moments, electric dipole moments, and other parity‐ violating effects. The ability to trap large numbers of atoms, >lo6, would make possible precision measurements

We present a laboratory-constructed mass spectrometer optimized for recording infrared multiple photon dissociation (IRMPD) spectra of mass-selected ions using a benchtop tunable infrared optical parametric oscillator∕amplifier (OPO∕A). The instrument is equipped with two ionization sources, an electrospray ionization source, as well as an electron ionization source for troubleshooting. This hybrid mass spectrometer is composed of a quadrupole mass filter for mass selection, a reduced pressure (∼10(-5) Torr) quadrupole ion trap (QIT) for OPO irradiation, and a reflectron time-of-flight drift tube for detecting the remaining precursor and photofragment ions. A helium gas pulse is introduced into the QIT to temporarily increase the pressure and hence enhance the trapping efficiency of axially injected ions. After a brief pump-down delay, the compact ion cloud is subjected to the focused output from the continuous wave OPO. In a recent study, we implemented this setup in the study of protonated tryptophan, TrpH(+), as well as collision-induced dissociation products of this protonated amino acid [W. K. Mino, Jr., K. Gulyuz, D. Wang, C. N. Stedwell, and N. C. Polfer, J. Phys. Chem. Lett. 2, 299 (2011)]. Here, we give a more detailed account on the figures of merit of such IRMPD experiments. The appreciable photodissociation yields in these measurements demonstrate that IRMPD spectroscopy of covalently bound ions can be routinely carried out using benchtop OPO setups.

We present infrared multiple photon dissociation (IRMPD) spectra in the hydrogen stretching region of the simplest b fragment, b(2) from protonated triglycine, contrasted to that of protonated cyclo(Gly-Gly). Both spectra confirm the presence of intense, diagnostic vibrations linked to the site of proton attachment. Protonated cyclo(Gly-Gly) serves as a reference spectrum for the diketopiperazine structure, showing a diagnostic O-H(+) stretch of the protonated carbonyl group at 3585 cm(-1). Conversely, b(2) from protonated triglycine exhibits a strong band at 3345 cm(-1), associated with the N-H stretching mode of the protonated oxazolone ring structure. Other weaker N-H stretches can also be discerned, such as the amino NH(2) and amide NH bands. These results demonstrate the usefulness of the hydrogen stretching region, and hence benchtop optical parametric oscillator/amplifier (OPO/A) set-ups, in making structural assignments of product ions in collision-induced dissociation (CID) of peptides.

Performing collinear laser spectroscopy on low intensity radioactive beams requires sensitive detection techniques. We explain our apparatus to detect atomic resonances in neutralized (208-210)Fr ion beams at beam energies of 5 keV and intensities of 10(5) s(-1). Efficient neutralization (or = 80%) is accomplished by passing the beam through a dense Rb vapor. Increased detection efficiency is achieved by amplitude modulating the exciting laser to decrease the scattered light background, allowing fluorescence detection only when the laser is near its minimum in the modulation cycle. Using this technique in a collinear geometry we achieve a background reduction by a factor of 180 and a signal-to-noise increase of 2.2, with the lifetime of the atomic state playing a role in the efficiency of this process. Such laser modulation will also produce sidebands on the atomic spectra which we illustrate.

Polarization and relaxation of radon isotopes by spin exchange with laser optically pumped rubidium were studied in preparation for electric dipole moment measurements with octupole deformed $^{223}\mathrm{Rn}$. \ensuremath{\gamma}-ray anisotropies provided a measure of nuclear polarization produced by spin exchange with laser polarized rubidium vapor, and the temperature dependence over the range 130 to ${220}^{\ifmmode^\circ\else\textdegree\fi{}}$C was measured to parametrize the spin exchange polarization and the quadrupole-dominated wall relaxation rate. These results provide quantitative data for developing electric dipole moment measurements of octupole-deformed $^{223}\mathrm{Rn}$ and other radon isotopes.

This corrects the article DOI: 10.1103/PhysRevLett.120.032701.