Prospects for Doppler cooling of three-electronic-level molecules

Abstract

Analogous to the extension of laser cooling techniques from two-level to three-level atoms, Doppler cooling of molecules with an intermediate electronic state is considered. In particular, we use a rate-equation approach to simulate cooling of SiO+, in which population buildup in the intermediate state is prevented by its short lifetime. We determine that Doppler cooling of SiO+ can be accomplished without optically repumping from the intermediate state, at the cost of causing undesirable parity flips and rotational diffusion. Since the necessary repumping would require a large number of continuous-wave lasers, optical pulse shaping of a femtosecond laser is proposed as an attractive alternative. Other candidate three-electron-level molecules are also discussed.Comment: 7 pages, 7 figure

Electronic spectroscopy of a cold SiO+ sample: Implications for optical pumping

“…Rotational cooling by this method was first demonstrated 9 with trapped AlH + . Other candidates with favorable properties for possible laser cooling in an ion trap were identified by Nguyen et al 15,18 , amongst them includes the focus of this study, the silicon monoxide cation, SiO + .…”

“…For the simplest implementation of broadband laser rotational cooling, near diagonal FCFs are important so that vibrational excitation is not likely to occur during the cooling process, although in some cases it should also be possible to re-pump vibrational excitations 15,18 [19][20][21][22][23] . In addition to electronic spectroscopy 19,20,22,24 , magnetic dipole allowed transitions between fine structure components of numerous rotational levels in the X 2  + (v=0) state were also measured by Rosner's group using a separated field optical pump/probes rf-double resonance technique 21 .…”

Resonant few-photon excitation of a single-ion oscillator

“…For instance, in our laboratory we are pursuing silicon monoxide ion (SiO + ) spectroscopy [19], where a single SiO + ion is cotrapped and sympathetically cooled by a Ba + ion. For SiO + the seeding laser would drive the dipole transition between |X 2 + , v = 0 and |B 2 + , v = 0 (λ = 385 nm) [20,21].…”

“…Implementation of sustained amplification with phase-sensitive detection, along with other technical improvements discussed above, could reduce scattering to the small number (order 100 and N = 1) required to make a seeded excitation detectable above the thermal and scattering noise. With a cotrapped fluorescing ion used for the amplification and detection, this motional seeding technique could be useful in spectroscopy experiments on molecular ions with semiclosed transitions [19,22,23], atomic ions with slow cycling transitions, and in bichromatic force schemes where cycling is enhanced by stimulated emission [24][25][26]. This resonant impulsive excitation technique could also be used to coherently excite selected normal modes of larger trapped ion crystals.…”

State-specific detection of trapped HfF+ by photodissociation

“…Quantum-state selective detection of molecular ions is a prerequisite for exciting new experiments in precision measurement [1,2], quantum information science [3], and astrochemistry [4]. Many proposed and ongoing precision measurement experiments utilize carefully chosen properties of molecules to improve previous constraints on fundamental symmetries and variations of constants set by experiments based on atoms [5,6,7,8].…”