Degenerate and two‐color resonant four‐wave mixing of C₂⁻ in a molecular beam environment

Abstract

In this paper, we demonstrate that degenerate and two-color resonant four-wave mixing spectroscopy is applicable for the sensitive and selective characterization of negative ions in a molecular beam environment. Results are shown for C − 2 , which is produced by discharging a mixture of acetylene and argon prior to supersonic expansion. Substantial signal-to-noise ratios of ≈150 show that the method is generally applicable for high-resolution optical double-resonance spectroscopy of negative ions. A detection sensitivity for C − 2 of ≈10 7 ions/cm 3 is estimated.

Unraveling the electronic structure of transition metal dimers using resonant four‐wave mixing

“…Our group has previously used TC‐RFWM and its one‐color analogue degenerate four‐wave mixing (DFWM) in the study of C 2 and C 3 among other molecules . In recent studies, the deperturbation of the v = 6 level of the d 3 Σ g state led to the discovery of the first quintet state of C 2 , 1 5 Σ g , which was then used as a gateway into the quintet manifold and allowed the measurement of the first quintet–quintet transition in dicarbon .…”

“…[28] Our group has previously used TC-RFWM and its one-color analogue degenerate four-wave mixing (DFWM) in the study of C 2 [29][30][31][32] and C 3 [33] among other molecules. [34][35][36][37][38][39] In recent studies, the deperturbation of the v = 6 level of the d 3 Σ g state led to the discovery of the first quintet state of C 2 , 1 5 Σ g , which was then used as a gateway into the quintet manifold and allowed the measurement of the first quintet-quintet transition in dicarbon. [30,32] These experiments were only made possible because of the selectivity of TC-RFWM as the measured transitions fell into the same spectral range as brighter, well-known transitions.…”

Deperturbation study of the state of C2 by applying degenerate and two-color resonant four-wave mixing

“…In fact, we have shown recently on several transient species (C 3 [28], C 2 [29], HC 4 S [29], HC 2 S [30] and C 2 À [31]) that the excellent sensitivity of TC-RFWM is applicable to the low-density environment of a discharged free-jet. From the combination of the two experimental techniques new possibilities ensue for an advanced treatment of the perturbation problem.…”

Photodetachment and Doppler laser cooling of anionic molecules

“…In comparison to atomic La − , molecular C 2 has a similar dipole transition but exhibits no unwanted photodetachment, no hyperfine structure and can be produced at low sub-eV kinetic energies [35]. Figure 1(a) shows an overview of the electronic and vibrational level structure of C 2 and C 2 .…”

“…2. Sympathetic Doppler cooling of C p 2 -C 2 can be produced from plasma discharge of acetylene with internal energies in the sub-eV range at densities of 10 13 m −3 [35,39]. After selection of C 2 in a mass spectrometer, the anions can be trapped in a Penning trap.…”