Observation of a gerade symmetry state of Cu₂ using two‐color resonant four‐wave mixing

Abstract

The first observation of an excited 0 + g state of dicopper is reported. "g" inversion symmetry states are not observable by direct one-photon absorption from the X 1 Σ + g ground state. Measurements are performed by applying nonlinear two-color resonant four-wave mixing (TC-RFWM) spectroscopy. Cold Cu 2 molecules in a molecular beam environment are generated by applying a pulsed laser vaporization source and subsequent near supersonic expansion of the vaporized metal plume entrained in a helium pulse. Spectra in the wavenumber region of the [37.5(v)]0 + g-B0 + u electronic transition are recorded by using the UNFOLDED double-resonance scheme. Specific rotational levels of the intermediate state B0 + u , v ′ = 1 are accessed from the X 1 Σ + g ground state. Dipole selection rules from the labeled levels define unambiguously the rotational quantum number and symmetry of the final state (ΔJ = ±0, 1 and g ↔ u). The UNFOLDED scheme is verified by additional measurements via the origin level, v ′ = 0, of the intermediate B0 + u state. Spectroscopic constants of the [37.5(v)]0 + g state have been determined for both 63 Cu 2 and 63 Cu 65 Cu isotopologues by analysis of the rotationally resolved spectra. The potential of TC-RFWM to study the unexplored "g" symmetry manifold of Cu 2 is discussed.

Development and applications of nonlinear optical spectroscopy: 18th ECONOS/38th ECW meeting in Rouen (France)

“…Gas-phase applications have also been a traditional field covered by ECONOS/ECW. Zhang et al [5] produced Cu dimers in a molecular beam and applied two-color resonant four-wave mixing spectroscopy to them. From their experiments, they reported the first observation DOI: 10.1002/jrs.5968 of an excited 0 + g state of dicopper.…”