2011-06,
Nguyen, Jason H.V.,
Viteri, C. Ricardo,
Hohenstein, Edward G.,
Sherrill, C. David,
Brown, Kenneth R.,
Odom, Brian
The direct laser cooling of neutral diatomic molecules in molecular
beams suggests that trapped molecular ions can also be laser cooled.
The long storage time and spatial localization of trapped molecular ions
provides an opportunity for multi-step cooling strategies, but also requires
careful consideration of rare molecular transitions. We briefly summarize the
requirements that a diatomic molecule must meet for laser cooling, and we
identify a few potential molecular ion candidates. We then carry out a detailed
computational study of the candidates BH+ and AlH+, including improved
ab initio calculations of the electronic state potential energy surfaces and
transition rates for rare dissociation events. On the basis of an analysis of
the population dynamics, we determine which transitions must be addressed
for laser cooling, and compare experimental schemes using continuous-wave
and pulsed lasers.