Cold highly charged ions in a cryogenic Paul trap

Abstract

Narrow optical transitions in highly charged ions (HCIs) are of particular interest for metrology and fundamental physics, exploiting the high sensitivity of HCIs to new physics. The highest sensitivity for a changing fine structure constant ever predicted for a stable atomic system is found in Ir17 + . However, laser spectroscopy of HCIs is hindered by the large (∼ 106 K) temperatures at which they are produced and trapped. An unprecedented improvement in such laser spectroscopy can be obtained when HCIs are cooled down to the mK range in a linear Paul trap. We have developed a cryogenic linear Paul trap in which HCIs will be sympathetically cooled by 9Be + ions. Optimized optical access for laser light is provided while maintaining excellent UHV conditions. The Paul trap will be connected to an electron beam ion trap (EBIT) which is able to produce a wide range of HCIs. This EBIT will also provide the first experimental input needed for the determination of the transition energies in Ir17 + , enabling further laser-spectroscopic investigations of this promising HC

Highly charged ions: Optical clocks and applications in fundamental physics

“…Recently, a combination of HCI production in an EBIT and sympathetic cooling inside of a Coulomb crystal of laser-cooled Be + ions contained in a linear RF trap (Schwarz et al, 2012;Versolato et al, 2013) has demonstrated how to bring the temperature of HCI by 8 orders of magnitude down to the mK regime, and opened the possibilities afforded by RF traps to the study of HCI. An artist's impression and schematic are shown in Figure 9 and Figure 10, respectively.…”

Atomic properties of Cd-like and Sn-like ions for the development of frequency standards and search for the variation of the fine-structure constant

“…Moreover, sympathetic cooling may be employed similar to the scheme used in Al + clock, which is cooled using lasercooled Be + or Mg + ions [1]. The experimental investigations toward the sympathetic cooling of HCIs and the precision laser spectroscopy of forbidden transitions are in progress [12][13][14][15]. A cooling scheme combining laser cooling of Be + ions and sympathetic cooling of Xe 44+ by Coulomb collisions with the cold Be + ions has been demonstrated in [16].…”

Identification of the Predicted5s−4fLevel Crossing Optical Lines with Applications to Metrology and Searches for the Variation of Fundamental Constants

“…In most of the proposed HCIs with atomic number Z ¼ 55-98 and in charge states from 7 to 35, the complex electronic structures are experimentally unknown, and accurate calculations are extremely difficult. In view of novel techniques for sympathetically cooling HCIs in Paul traps [13][14][15] aiming at quantum logic spectroscopy on highly forbidden transitions [16], such data are urgently required.Observations from quasar absorption spectra have suggested a spatial variation of the value of the fine-structure constant α over cosmological dimensions [17], characterized by a dipolar distribution with a value of 10 −6 GLyr −1 . Laboratory experiments [18][19][20][21] have not yet reached the accuracy needed to test this dipolar pattern, which translates to a temporal variation of 10 −19 yr −1 [22] due to the motion of the Earth.…”

“…In most of the proposed HCIs with atomic number Z ¼ 55-98 and in charge states from 7 to 35, the complex electronic structures are experimentally unknown, and accurate calculations are extremely difficult. In view of novel techniques for sympathetically cooling HCIs in Paul traps [13][14][15] aiming at quantum logic spectroscopy on highly forbidden transitions [16], such data are urgently required.…”

“…Nonetheless, at level crossings with two or more nearly degenerate electronic configurations, forbidden, and thus narrow, optical transitions with an enhanced sensitivity [1,2] arise. In particular, the Nd-like system Ir 17þ offers narrow lines between three electronic configurations 4f 14 , 4f 13 5s 1 , and 4f 12 5s 2 with the highest ever predicted sensitivity in a stable atomic system [2]. However, calculations for this system are exceptionally difficult, and the predicted energies for intraconfiguration M1 transitions ideally suited for clock applications [6] can exhibit errors on the 10% level, as can be seen below.…”