RESUMO
Ro-vibronic spectra of the 13C18O carbon monoxide isotopologue were obtained with (i) emission spectroscopy in the visible region using a Bruker IFS 125HR spectrometer (University of Rzeszów) and (ii) vacuum-ultraviolet absorption spectroscopy using the wave-front-division spectrometer on the DESIRS beamline of the SOLEIL synchrotron. A deperturbation analysis of the 13C18O A1Π(v = 1) level was conducted from 598 observed transitions from the B1Σ+ - A1Π(0, 1), C1Σ+ - A1Π(0, 1), A1Π - X1Σ+(1, 0), B1Σ+ - X1Σ+(0, 0), C1Σ+ - X1Σ+(0, 0), I1Σ- - X1Σ+(2, 0) bands and five further nominally forbidden bands. An effective Hamiltonian and term-value fitting analysis was implemented. Consequently, 135 parameters were floated: 23 molecular parameters, including molecular constants for A1Π(v = 1), I1Σ-(v = 2), d3Δ(v = 6), e3Σ-(v = 3) and D1Δ(v = 1); rotation-electronic (L-uncoupling) mixing of A1Π(v = 1) â¼ [D1Δ(v = 1), I1Σ-(v = 1), I1Σ-(v = 2)] and spin-orbit interaction parameters for A1Π(v = 1) â¼ [d3Δ(v = 6), e3Σ-(v = 3), a'3Σ+(v = 11)]; the spin-orbit/spin-electronic/L-uncoupling a3Π(v = 12) â¼ d3Δ(v = 5) and spin-orbit a3Π(v = 12) â¼ [D1Δ(v = 1), I1Σ-(v = 2)] perturbation parameters; as well as 112 ro-vibronic term values of B1Σ+(v = 0) up to J = 50 and C1Σ+(v = 0) up to J = 60. The significant, indirect a3Π(v = 12) â¼ [e3Σ-(v = 2, 3), d3Δ(v = 5, 6)] â¼ A1Π(v = 1) spin-orbit/spin-electronic/L-uncoupling interaction and a3Π(v = 12) â¼ [I1Σ-(v = 2), D1Δ(v = 1)] â¼ A1Π(v = 1) spin-orbit/L-uncoupling interaction were detected and analysed. Thus, this study, using modern experimental methods and deperturbation analysis, leads to a much improved description in terms of molecular constants and interaction parameters, compared to previous studies of the A1Π(v = 1) energy region in the 13C18O isotopologue. This research is a continuation of the studies on the A1Π state and its numerous perturbers in the CO isotopologues made by our team.
