Optical Pumping of TeH+: Implications for the Search for Varying mp/me

Abstract

Molecular overtone transitions provide optical frequency transitions sensitive to variation in the proton-to-electron mass ratio ( μ ≡ m p / m e ). However, robust molecular state preparation presents a challenge critical for achieving high precision. Here, we characterize infrared and optical-frequency broadband laser cooling schemes for TeH + , a species with multiple electronic transitions amenable to sustained laser control. Using rate equations to simulate laser cooling population dynamics, we estimate the fractional sensitivity to μ attainable using TeH + . We find that laser cooling of TeH + can lead to significant improvements on current μ variation limits.

In search of molecular ions for optical cycling: a difficult road

“…However, the efforts to identify molecular ions suitable for optical cycling have been limited. Odom, Brown, and co-workers have explored optical cycling in AlH + , 30-32 BH + , 33 SiO + , 34,35 and TeH + , 36 often with an eye towards precision measurement. Other molecular ions have been studied theoretically including both cations [37][38][39][40] and anions [41][42][43] .…”

Molecular lattice clock with long vibrational coherence

“…Molecules possess a more extensive set of internal degrees of freedom than atoms including vibrations and rotations. A clock based on molecular vibrations can access fundamental measurements that are out of reach for atomic clocks [18][19][20][21][22][23][24]. These include searches for new forces [25], modelindependent tests of the electron-to-proton mass ratio stability [26], and tests of quantum electrodynamics in bound systems [27,28].…”

Cooling of a Zero-Nuclear-Spin Molecular Ion to a Selected Rotational State

“…Further refinements may enable efficient fluorescent imaging or direct Doppler cooling of SiO + [29,32]. Such improvements could help realize multi-ion molecular clocks with canceling Stark and second order Doppler shifts [45].…”

“…3 and inset are used to determine the fidelity of ground state preparation and an equivalent temperature. Also shown are the results of an Einstein rate equation simulation [45] using the experimental spectral intensity and spectral cutoff sharpness of the cooling laser, with SiO + initialized to a 300 K distribution. Systematic shifts, which predict an offset between raw data and the simulation, include reaction with the background hydrogen, impure isotope selection, and partial spectral overlap of the laser linewidth with other dissociating transitions.…”