Decay Rate Measurement of the First Vibrationally Excited State ofMgH+in a Cryogenic Paul Trap

Abstract

We present a method to measure the decay rate of the first excited vibrational state of polar molecular ions that are part of a Coulomb crystal in a cryogenic linear Paul trap. Specifically, we have monitored the decay of the |ν = 1, J = 1)(X) towards the |ν = 0, J = 0)(X) level in MgH+ by saturated laser excitation of the |ν = 0, J = 2)(X)-|ν = 1, J = 1)(X) transition followed by state selective resonance enhanced two-photon dissociation out of the |ν = 0, J=2)(X) level. The experimentally observed rate of 6.32(0.69) s(-1) is in excellent agreement with the theory value of 6.13(0.03) s(-1) (this Letter). The technique enables the determination of decay rates, and thus absorption strengths, with an accuracy at the few percent level.

Broadband optical cooling of molecular rotors from room temperature to the ground state

“…Similarly to the approach used in Ref. 29, the vibrational lifetime τ can be extracted from the time-dependent population. The fit described in Methods yields τ = 140 (20) ms, in good agreement with the theory value of 127 ms [22].…”

Vibronic Spectroscopy of Sympathetically Cooled CaH+

“…By using a 1+2' resonance enhanced multi-photon dissociation scheme, it is possible to measure the fundamental rovibrational transitions in the 1 1 Σ state by sweeping the frequency of the first photon from a 6.9 µm laser. The second photon would excite to one of the 2 1 Σ vibrational states, and the third photon would dissociate the molecules [4,37]. An IR laser source with a wide tuning frequency would enable the measurement of multiple overtones as well.…”

Reversing hydride-ion formation in quantum-information experiments withBe+

“…[18]. Given the difficulty of detecting scattered photons from dilute molecular-ion samples, rotational-state-selective PD has emerged as a critical tool for molecular ion spectroscopy [15,19] and precision measurements [16,20], while rotationally-insensitive dissociation schemes provide valuable tests of molecular * Electronic address: brian.sawyer@boulder.nist.gov ) after 9000 pulses of 157 nm photodissociation light at 1.6 mJ/pulse. We measure an increase in the Be + fraction from 81% to 97% of the constant total ion number in the crystal.…”

“…Recent experimental demonstrations with trapped heteronuclear diatomic molecular ions include MgH + [9,12], CaH + /CaD + [13], HD + [14], AlH + [15], HfF + [16], SrCl + [17], and BaCl + [18]. Given the difficulty of detecting scattered photons from dilute molecular-ion samples, rotational-state-selective PD has emerged as a critical tool for molecular ion spectroscopy [15,19] and precision measurements [16,20] theory [13,17,18]. The work described here is the first experimental photodissociation of BeH + .…”