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arXiv:2603.00282 · Physical Review A

Hyperfine spectroscopy and laser cooling of the fermionic isotopes Ti 47 and Ti 49

Jackson Schrott, Scott Eustice, Pouya Sadeghpour, Rowan Duim, Hiromitsu Sawaoka, Dmytro Filin, Marianna S. Safronova, Dan Stamper-Kurn

Published May 21, 2026• 1 citation
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Abstract

We report on magneto-optical trapping of the two fermionic isotopes of atomic titanium, $^{47}$Ti and $^{49}$Ti. Unlike the even mass-number isotopes, which were recently laser cooled, $^{47}$Ti and $^{49}$Ti have nonzero nuclear spins and, consequently, their atomic levels are split by hyperfine structure. Combining and comparing theoretical calculations and atomic beam-spectroscopy measurements, we determine the hyperfine structures and isotope shifts of the $\mathrm{3d^24s^2}$ $\mathrm{a^3F_4\rightarrow 3d^2(^3P)4s4p(^3P^o)}$ $\mathrm{y^5D_4^o}$ optical-pumping transition at optical wavelength 391nm and the $\mathrm{3d^3(^4F)4s}$ $\mathrm{a^5F_5\rightarrow 3d^3(^4F)4p}$ $\mathrm{y^5G_6^o}$ laser-cooling transition at wavelength 498nm. With this information, we produce magneto-optical traps of both $^{47}$Ti and $^{49}$Ti by applying two additional tones of light to repump atoms to the maximum-spin states on the laser-cooling transition. Directly loading from the atomic flux of a titanium sublimation pump, we produce $^{47}$Ti and $^{49}$Ti traps with 731(190) and 1142(240) atoms, and with lifetimes of 330(15)ms and 310(8)ms, respectively.

DOI
10.1103/fsn1-cdv4

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We report on magneto-optical trapping of the two fermionic isotopes of atomic titanium, 47^{47}47Ti and 49^{49}49Ti. Unlike the even mass-number isotopes, which were recently laser cooled, 47^{47}47Ti and 49^{49}49Ti have nonzero nuclear spins and, consequently, their atomic levels are split by hyperfine structure. Combining and comparing theoretical calculations and atomic beam-spectroscopy measurements, we determine the hyperfine structures and isotope shifts of the 3d24s2\mathrm{3d^24s^2}3d24s2 a3F4→3d2(3P)4s4p(3Po)\mathrm{a^3F_4\rightarrow 3d^2(^3P)4s4p(^3P^o)}a3F4​→3d2(3P)4s4p(3Po) y5D4o\mathrm{y^5D_4^o}y5D4o​ optical-pumping transition at optical wavelength 391nm and the 3d3(4F)4s\mathrm{3d^3(^4F)4s}3d3(4F)4s a5F5→3d3(4F)4p\mathrm{a^5F_5\rightarrow 3d^3(^4F)4p}a5F5​→3d3(4F)4p y5G6o\mathrm{y^5G_6^o}y5G6o​ laser-cooling transition at wavelength 498nm. With this information, we produce magneto-optical traps of both 47^{47}47Ti and 49^{49}49Ti by applying two additional tones of light to repump atoms to the maximum-spin states on the laser-cooling transition. Directly loading from the atomic flux of a titanium sublimation pump, we produce 47^{47}47Ti and 49^{49}49Ti traps with 731(190) and 1142(240) atoms, and with lifetimes of 330(15)ms and 310(8)ms, respectively.
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We realize a magneto-optical trap (MOT) of titanium (Ti) atoms, performing laser cooling on the 498 nm transition between the long-lived 3 d 3 ( F 4 ) 4 s a 5 F 5 metastable state and the 3 d 3 ( F 4 ) 4 p y 5 G 6 o excited state. Without the addition of any repumping light, we observe MOTs of the three stable, I = 0 bosonic isotopes, Ti 46 , Ti 48 , and Ti 50 . Up to 8.30 ( 26 ) × 10 5 Ti 48 atoms are trapped at a maximum density of 1.3 ( 4 ) × 10 11 cm − 3 and at a temperature of 90 ( 15 ) µ K . By measuring the decay of the MOT, we constrain the leakage branching ratio of the cooling transition ( ≤ 2.5 × 10 − 6 ) and the two-body loss coefficient ( ≤ 2 × 10 − 10 cm 3 s − 1 ). Our approach to laser cooling Ti can be applied to other transition metals, enabling a significant expansion of the elements that can be laser cooled.
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