Laser spectroscopy of indium Rydberg atom bunches by electric field ionization

Abstract

This work reports on the application of a novel electric field-ionization setup for high-resolution laser spectroscopy measurements on bunched fast atomic beams in a collinear geometry. in combination with multi-step resonant excitation to Rydberg states using pulsed lasers, the field ionization technique demonstrates increased sensitivity for isotope separation and measurement of atomic parameters over previous non-resonant laser ionization methods. The setup was tested at the Collinear Resonance Ionization Spectroscopy experiment at ISOLDE-CERN to perform highresolution measurements of transitions in the indium atom from the 5s 2 5d 2 D 5/2 and 5s 2 5d 2 D 3/2 states to 5s 2 np 2 p and 5s 2 nf 2 F Rydberg states, up to a principal quantum number of n = 72. The extracted Rydberg level energies were used to re-evaluate the ionization potential of the indium atom to be 46, 670.107(4) cm −1. The nuclear magnetic dipole and nuclear electric quadrupole hyperfine structure constants and level isotope shifts of the 5s 2 5d 2 D 5/2 and 5s 2 5d 2 D 3/2 states were determined for 113,115 In. The results are compared to calculations using relativistic coupled-cluster theory. A good agreement is found with the ionization potential and isotope shifts, while disagreement of hyperfine structure constants indicates an increased importance of electron correlations in these excited atomic states. With the aim of further increasing the detection sensitivity for measurements on exotic isotopes, a systematic study of the field-ionization arrangement implemented in the work was performed at the same time and an improved design was simulated and is presented. the improved design offers increased background suppression independent of the distance from field ionization to ion detection. The ability to separate and study small quantities of isotopes from a large ensemble without losses is the limiting factor of many experimental studies in modern nuclear physics 1-4 , as exotic isotopes of interest can often only be produced at low rates (fewer than 100s of ions per second) and their accumulation into substantial quantities is prevented by their short half-lives. Furthermore, sensitive detection or separation of small quantities of isotopes also has numerous technological applications 5-11. Fast beam collinear laser spectroscopy techniques have allowed high-precision measurements on short-lived isotopes, down to rates of fewer than 100 ions per second 3,12,13. These approaches use the Doppler compression of an accelerated atomic beam to enable high-precision laser spectroscopy measurements to be performed in a collinear geometry 14,15. This technique is now being implemented at radioactive ion beam facilities worldwide, giving a resolution of a few 10s of MHz, which is sufficient to resolve the hyperfine structure for nuclear physics studies 16-19. Motivated by a need for higher sensitivity to access exotic isotopes produced at rates lower than a few ions per second, a variation of the technique, the Collinear Resonance Ionization Spectr...

Evolution of nuclear charge radii in copper and indium isotopes *

“…Plenty of methods are employed to derive the nuclear size, such as high-energy elastic electron scattering ( ) [25,26], muonic atom X-rays ( ) [27][28][29], high-resolution laser spectroscopy [30], highly-sensitive Collinear Resonance Ionization Spectroscopy (CRIS) [31,32], optical isotope shifts (OIS) and K α X-ray isotope shifts (K α IS) [33]. Furthermore, the values of charge radii can also be extracted indirectly from the experimental observables of α-decay properties [34][35][36][37][38] and cluster or proton emission data [39].…”

Evolution of nuclear charge radii in copper and indium isotopes

“…Plenty of experimental methods with different sources are employed to derive the nuclear size, for instance, high-energy elastic electron scattering (e − ) [24,25], muonic atom Xrays (u − ) [26][27][28], high-resolution laser spectroscopy (GSI) [29], optical isotopes shift (OIS) and K α X-rays isotopes shift (K α IS) [30], highly-sensitive Collinear Resonance Ionization Spectroscopy (CRIS) [31,32]. Besides, the quantities of charge radii can also be extracted indirectly from the experimental observations of nuclear decay , such as α-decay properties [33][34][35][36][37], cluster or proton emission data [38].…”

Nuclear charge radii of Na isotopes: A tale of two theories

“…These proved to have several limitations as detailed in Refs. [45,46]. The analytic response-based RCC (AR-RCC) theory was developed to circumvent these problems.…”

“…Recently, we have used the AR-RCC theory with singles and doubles approximation (AR-RCCSD) to estimate the IS constants for transitions in the indium atom [38,45], but calculations for Na and Mg + require further development to precisely estimate these constants by including higher-order electron correlations. Thus we extend our AR-RCC theory to account for full triples excitations (AR-RCCSDT method).…”