Radiative Rotational Lifetimes and State-Resolved Relative Detachment Cross Sections from Photodetachment Thermometry of Molecular Anions in a Cryogenic Storage Ring

Abstract

Photodetachment thermometry on a beam of OH^{-} in a cryogenic storage ring cooled to below 10 K is carried out using two-dimensional frequency- and time-dependent photodetachment spectroscopy over 20 min of ion storage. In equilibrium with the low-level blackbody field, we find an effective radiative temperature near 15 K with about 90% of all ions in the rotational ground state. We measure the J=1 natural lifetime (about 193 s) and determine the OH^{-} rotational transition dipole moment with 1.5% uncertainty. We also measure rotationally dependent relative near-threshold photodetachment cross sections for photodetachment thermometry.

Vibrational overtone spectroscopy of cold trapped hydroxyl anions

“…The s-wave threshold detachment of OH − has been extensively studied through photodetachment [27,28] and deviations from the Wigner threshold law have been observed due to the electron-dipole interaction [29,30]. With its large rotational constant, OH − has also been used to probe the rotational thermalization by buffer gas cooling [26,31] and in cryogenic storage rings [32,33]. In buffer gas at low temperatures, significant deviations of the rotational temperature from the thermal bath have been seen [34].…”

Collisional relaxation kinetics fororthoandparaNH2−under photodetachment in cold ion traps

“…Generally, the collision-induced internal quenching is far more efficient for rotations than for vibrations, while vibrations are more efficiently quenched by radiative transitions. [9][10][11] In the present work we investigate the rotational quenching kinetics for a triatomic molecular ion. Recently we studied the absolute inelastic collision rate coefficient for the diatomic molecular anion OH À .…”

Roadmap on dynamics of molecules and clusters in the gas phase

“…with lasers) for experiments. The preparation of beams of small molecular ions with nearly all of them in a single ro-vibrational quantum state has been demonstrated for OH − at both CSR and DESIREE [195,196]. Diatomic molecules, such as OH − , have only one possible conformation, while larger molecules may have many different forms.…”