M. Hammen

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Marc Champagne

Kwantlen Polytechnic University

Remo Caponi

University of Cologne

Armando Marques-Guedes

UNL - New University of Lisbon

María Ruiz Ortiz

Universidad Internacional de Valencia

Matthew J Sharpe

Australian Catholic University

Miguel Barreto Henriques

Pontificia Universidad Javeriana

Catalina Quesada-Gómez

University of Miami

Adolfo Vasquez Rocca

Universidad Complutense de Madrid

Diego Villar

National Scientific and Technical Research Council

Lorena Córdoba

National Scientific and Technical Research Council

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Papers by M. Hammen

Unexpectedly large charge radii of neutron-rich calcium isotopes

Nature Physics, 2016

TRIGA-SPEC: the prototype of MATS and LaSpec

Journal of Physics: Conference Series, 2015

ABSTRACT Investigation of short-lived nuclei is a challenging task that MATS and LaSpec will hand... more ABSTRACT Investigation of short-lived nuclei is a challenging task that MATS and LaSpec will handle at the low energy branch of Super-FRS at FAIR. The groundwork for those experiments is laid-out already today at the TRIGA-SPEC facility as a powerful development platform located at the research reactor TRIGA Mainz. The latest status, new developments and first results of commissioning runs are presented here.

Methods for non-timber forest products research: the tropenbos experience

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Ground-state electromagnetic moments of calcium isotopes

by Ronald Ruiz, M. Hammen, and J. Menéndez

Physical Review C, 2015

High-resolution bunched-beam collinear laser spectroscopy was used to measure the optical hyperfi... more High-resolution bunched-beam collinear laser spectroscopy was used to measure the optical hyperfine spectra of the 43−51 Ca isotopes. The ground state magnetic moments of 49,51 Ca and quadrupole moments of 47,49,51 Ca were measured for the first time, and the 51 Ca ground state spin I = 3/2 was determined in a model-independent way. Our results provide a critical test of modern nuclear theories based on shell-model calculations using phenomenological as well as microscopic interactions. The results for the neutron-rich isotopes are in excellent agreement with predictions using interactions derived from chiral effective field theory including three-nucleon forces, while lighter isotopes illustrate the presence of particle-hole excitations of the 40 Ca core in their ground state.

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Laser Spectroscopy of Cadmium Isotopes: Probing the Nuclear Structure Between the Neutron 50 and 82 Shell Closures

Nuclear charge radii of magnesium isotopes by laser spectroscopy with combined fluorescence and beta-decay detection

Laser spectroscopy on relativistic 209 Bi 82+ and 209 Bi 80+ ions at the ESR storage ring of the GSI

Test of QED in strong magnetic fields by laser spectroscopy of the hyperfine structure of Bi 82+ and Bi 80+

Optical measurement of the longitudinal ion distribution of bunched ion beams in the ESR

Nuclear Instruments & Methods in Physics Research Section a-Accelerators Spectrometers Detectors and Associated Equipment, 2013

ABSTRACT An optical technique to study the longitudinal distribution of ions in a bunched ion bea... more ABSTRACT An optical technique to study the longitudinal distribution of ions in a bunched ion beam circulating in a storage ring is presented. It is based on the arrival-time analysis of photons emitted after collisional excitation of residual gas molecules. The beam-induced fluorescence was investigated in the ultraviolet regime with a channeltron and in the visible region using a photomultiplier tube. Both were applied to investigate the longitudinal shape of bunched and electron-cooled 209Bi80+ ion beams at about 400 MeV/u in the experimental storage ring (ESR) at GSI Helmholtzzentrum für Schwerionenforschung in Darmstadt, Germany. Bunch lengths were determined with an uncertainty of about 0.5 m using the UV-sensitive channeltron and with slightly lower accuracy from the photomultiplier data due to the slower transitions in the red region of the spectrum. The Gaussian shape of the longitudinal distribution of ions inside the bunch was confirmed. With the information of the transverse beam size that can be measured simultaneously by a newly installed ionization profile monitor (IPM) at the ESR, an accurate determination of the ion density in the bunched beam will be allowed.

$Research paper thumbnail of Nuclear Charge Radius of ^{12}Be$

Nuclear Charge Radius of ^{12}Be

Physical Review Letters, 2012

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

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$Research paper thumbnail of Spins, Electromagnetic Moments, and Isomers of ^{107-129}Cd$

Spins, Electromagnetic Moments, and Isomers of ^{107-129}Cd

Physical Review Letters, 2013

The neutron-rich isotopes of cadmium up to the N=82 shell closure have been investigated by high-... more The neutron-rich isotopes of cadmium up to the N=82 shell closure have been investigated by high-resolution laser spectroscopy. Deep-uv excitation at 214.5 nm and radioactive-beam bunching provided the required experimental sensitivity. Long-lived isomers are observed in (127)Cd and (129)Cd for the first time. One essential feature of the spherical shell model is unambiguously confirmed by a linear increase of the 11/2(-) quadrupole moments. Remarkably, this mechanism is found to act well beyond the h(11/2) shell.

Tests of atomic charge-exchange cells for collinear laser spectroscopy

Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 2012

The performance characteristics of two charge-exchange cells (CECs) with horizontal and vertical ... more The performance characteristics of two charge-exchange cells (CECs) with horizontal and vertical cell configurations were determined by neutralizing a 10-keV rubidium ion beam in a potassium vapor. The neutralization efficiency and the fluorescence line shape of the 5s 2 S 1=2 25p 2 P 3/2 (D 2 ) transition in neutral 85 Rb were investigated as a function of the reservoir temperature used to control the potassium vapor density. The CECs exhibited similar neutralization performance and at neutralization efficiencies greater than 25-50% an asymmetric line shape of the rubidium D 2 fluorescent signal was observed. The asymmetry was attributed to inelastic channels in the charge-exchange process. The rubidium D 2 fluorescence line shape was fitted with a multiple Voigt function, which quantitatively models the inelastic channels. In the present Rb þ þ K charge-exchange process, the optimum neutralization efficiency to accurately determine the centroid of the Rb D 2 resonance line shape was obtained by fitting single Voigt functions to the resonance spectra obtained at neutralization efficiencies where inelastic processes were negligible.

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An RFQ cooler and buncher for the TRIGA-SPEC experiment

Applied Physics B, 2014

ABSTRACT A linear Paul trap for cooling of ion beams, the former cooler for emittance elimination... more ABSTRACT A linear Paul trap for cooling of ion beams, the former cooler for emittance elimination radiofrequency quadrupole (RFQ) at MISTRAL/ISOLDE, has been installed and commissioned at the TRIGA-SPEC experiment located at the research reactor TRIGA Mainz. It is connected to a hot-surface-ionization ion source and a subsequent mass separator for ionization and pre-separation of neutron-rich fission products as delivered from the reactor. The capability of accumulating and bunching ion beams has been implemented to provide low-emittance ion pulses of 250 ns width containing up to 106 ions. A technical description of the upgraded RFQ as well as its characterization with stable ions is presented. Its installation allows delivery of low-emittance ion bunches to the two branches of the TRIGA-SPEC experiment, namely TRIGA-TRAP and TRIGA-LASER.

La construcción del patrimonio como lugar: Un estudio de caso en Bogotá

by M. Hammen and Dolly C Palacio-Tamayo

Antípoda: Revista de …, 2009

a n T Í P o d a n º 8 | e n e r o -j U n i o 2 0 0 9 6 2 De sde hace varios siglos se ha intentad... more a n T Í P o d a n º 8 | e n e r o -j U n i o 2 0 0 9 6 2 De sde hace varios siglos se ha intentado definir el patrimonio con el fin de conservarlo. Una primera manifestación de esta preocupación se presenta en el Renacimiento occidental, pero esta se desarrolla, especialmente, a partir del siglo XIX. Poco a poco se va a hablar no sólo de patrimonio construido, sino del natural, y, más recientemente, de patrimonio tangible e intangible, material e inmaterial. En varias partes del mundo, durante las últimas décadas, muchos elementos se han vuelto patrimonio 2 : desde los monumentos y edificios puntuales con función de memoria, los conjuntos de edificios, los centros históricos de ciudades o pueblos, hasta los paisajes, las fábricas, los oficios, etc. Es decir, se han incluido hasta elementos que en otros tiempos hubieran sido totalmente extraños a cualquier consideración de clase conservacionista. Más aún, hoy en día se declaran patrimonio elementos que tienen pocos años de existencia. De tal forma, si de un lado se tiende a incluir casi de forma enfermiza todo lo legado, del otro se ve también cómo la noción misma puede ser muy volátil.

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Unexpectedly large charge radii of neutron-rich calcium isotopes

Nature Physics, 2016

TRIGA-SPEC: the prototype of MATS and LaSpec

Journal of Physics: Conference Series, 2015

Methods for non-timber forest products research: the tropenbos experience

Download

Ground-state electromagnetic moments of calcium isotopes

by Ronald Ruiz, M. Hammen, and J. Menéndez

Physical Review C, 2015

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Laser Spectroscopy of Cadmium Isotopes: Probing the Nuclear Structure Between the Neutron 50 and 82 Shell Closures

Nuclear charge radii of magnesium isotopes by laser spectroscopy with combined fluorescence and beta-decay detection

Laser spectroscopy on relativistic 209 Bi 82+ and 209 Bi 80+ ions at the ESR storage ring of the GSI

Test of QED in strong magnetic fields by laser spectroscopy of the hyperfine structure of Bi 82+ and Bi 80+

Optical measurement of the longitudinal ion distribution of bunched ion beams in the ESR

Nuclear Instruments & Methods in Physics Research Section a-Accelerators Spectrometers Detectors and Associated Equipment, 2013

$Research paper thumbnail of Nuclear Charge Radius of ^{12}Be$

Nuclear Charge Radius of ^{12}Be

Physical Review Letters, 2012

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$Research paper thumbnail of Spins, Electromagnetic Moments, and Isomers of ^{107-129}Cd$

Spins, Electromagnetic Moments, and Isomers of ^{107-129}Cd

Physical Review Letters, 2013

Tests of atomic charge-exchange cells for collinear laser spectroscopy

Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 2012

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An RFQ cooler and buncher for the TRIGA-SPEC experiment

Applied Physics B, 2014

La construcción del patrimonio como lugar: Un estudio de caso en Bogotá

by M. Hammen and Dolly C Palacio-Tamayo

Antípoda: Revista de …, 2009

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