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Fabian C. Pastrana Cruz

Publications and source records attributed to Fabian C. Pastrana Cruz.

2 recordsLinked to original sources

CREMA: Collinear Resonance for Exotic Molecules and Atoms

The Collinear Resonance for Exotic Molecules and Atoms (CREMA) setup has been developed and commissioned at the Massachusetts Institute of Technology's Laboratory for Nuclear Science. The instrument combines the Doppler-suppressed resolution of the collinear fast-beam geometry with the selectivity of resonance ionization, for precision measurements of hyperfine structure and isotope shifts in atoms and molecules. We describe the setup, including the ion-optical simulations in which a multi-objective evolutionary algorithm provided the starting settings for the beam transport, and report commissioning measurements of the hyperfine structure of 133Cs. The extracted hyperfine constants agree with literature values within one standard deviation, demonstrating the operational readiness of the setup. CREMA mirrors the Resonance Ionization Spectroscopy Experiment at the Facility for Rare Isotope Beams and serves as its offline counterpart for the development of laser ionization schemes and techniques for future studies of exotic atoms and molecules.

nucl-ex↗

Isotope-shift factors with quantum electrodynamics effects for many-electron systems: A study of the nuclear charge radius of $^{26m}$Al

A method for calculating the field shift contribution to isotope shifts in many-electron atoms, incorporating quantum electrodynamics (QED) effects, is introduced. We also implement the model QED approach to incorporate QED contribution to the nuclear recoil effect at the high-order correlation effects treatment level. The proposed computational scheme is used to revise the value of the root-mean-square (rms) nuclear charge radius of the isomer of aluminium-26, $^{26m}$Al. This radius is important for the global analysis of the $V_{ud}$ element of the Cabibbo-Kobayashi-Maskawa matrix. The difference in mean-square nuclear charge radii of $^{27}$Al and $^{26m}$Al, obtained by combining the calculated atomic factors with recently measured isotope shift (IS) of the $3s^23p~^2P_{3/2} \to 3s^24s~^2S_{1/2}$ transition in Al, is $0.443(44)(19)~{\rm fm}^2$, where the first and second uncertainties are experimental and theoretical ones, respectively. The latter is reduced by a factor of 4 with respect to the previous study. Using this value and the known value of the rms charge radius of $^{27}$Al, the resultant value $R_c(^{26m}$Al) = 3.132(10)~fm is obtained. With the improved accuracy of the calculated IS factors the error in $R_c(^{26m}$Al) is now dominated by the experimental uncertainty. Similar revision of rms charge radii is made for the $^{28}$Al, $^{29}$Al, $^{30}$Al, $^{31}$Al and $^{32}$Al isotopes using existing IS measurements. Additionally, atomic factors are computed for the $3s^23p~^2P_{3/2} \to 3s^24s~^2S_{1/2}$, $3s^23p~^2P_{1/2} \to 3s^25s~^2S_{1/2}$ and $3s^23p~^2P_{3/2} \to 3s^25s~^2S_{1/2}$ transitions in Al, which can be used in future experimental studies.

physics.atom-ph↗