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

Abstract

<p>Optical cycling, a continuous photon scattering off atoms or molecules, plays a central role in the quantum information science. While optical cycling has been experimentally achieved for many neutral species,...</p>

Photon spin molasses for laser cooling molecular rotation

“…As an example, we can consider the specific case of YF + . This molecule possess a moderate rotational constant (B ≈ 8.7 GHz), a strong C 2 Π ← X 2 Σ + band (γ/2π ≈ 37 MHz) with predicted diagonal FCF > 0.999 [25], and reasonable transition wavelengths for pulsed-laser excitation (∆E C−X ≈ 4.0 eV). To asses the rotational cooling effect of photon spin molasses in isolation, we neglect the intermediate electronic states that provide alternative decay paths in this species, though these are present in some species that have been successfully laser cooled [27].…”

“…Here, the term in parentheses on the left can be identified as 2/µ from the general treatment in the previous section, and we find that the momentum damping coefficient is smaller than the classical model by a factor of 6: 3× from the polarization switching and 2× from the rotation of the dipole moment in the lab frame (see Eqs. (24)(25)). We find the equilibrium J ≡ J 0 by setting Ė = 0, which gives…”

“…( 16). For τ p ≈ 10 ps pulses, the Doppler limiting temperature is T ≈ 1 K. This technique could be useful for cooling small molecular ions, including those that appear promising for quantum science applications [25,26]. At least some of the identified molecules possess features desirable for optical cycling, e.g.…”

“…At least some of the identified molecules possess features desirable for optical cycling, e.g. short radiative lifetimes and nearly-diagonal Franck-Condon factors (FCFs) [25]. Moreover, it is relatively straightforward to trap molecular ions with long trapping lifetimes.…”

Calculation of Spin–orbit Couplings Using RASCI Spinless One-Particle Density Matrices: Theory and Applications

“…[77][78][79] More recently, small diatomics are attracting considerable attention in the context of laser cooling experiments and quantum information science. [80] BH and AlH have been investigated using different spectroscopies [81][82][83] and simulations. [84] These studies corroborated diradical nature of their ground states.…”