Accidental predissociation phenomena in the E 1Π, v=0 and v=1 states of 12C16O and 13C16O

Abstract

We have studied vϭ0 and vϭ1 levels of the E 1 ⌸ state of CO in excitation from the ground state by one-and two-photon transitions, thus probing e and f ⌳-doublet components. New accidental predissociations were found in the E 1 ⌸, vϭ0 state for high J values ͑J e ϭ41, 44 for 12 C 16 O and J e ϭ41, 50 for 13 C 16 O͒. The predissociation phenomenon in the E 1 ⌸, vϭ1 state at Jϭ7 was reinvestigated and for both e and f components also Jϭ9, 10, and 12 were found to be perturbed. Perturbations by all three spin components of a k 3 ⌸, vϭ5 state were deduced. Furthermore the accidental predissociation in E 1 ⌸, vϭ0 J e ϭ31 was reinvestigated. Measurements of spectral line shifts were modeled assuming a spin-orbit coupling between E 1 ⌸ and the 3 ⌸ 1 component of the k 3 ⌸ state. Relative predissociation lifetimes of k 3 ⌸, vϭ3 and 5 with respect to E 1 ⌸, vϭ0 and vϭ1 are deduced from an analysis of observed intensity effects. For the E 1 ⌸, vϭ1 state rotational state dependent lifetimes were determined at low-J values. Line positions of CO lines were calibrated on an absolute frequency scale within 0.05 cm Ϫ1 against the tellurium and iodine standard in the visible. Accurate molecular constants for the E 1 ⌸, vϭ0 and vϭ1 states are determined for both 12 C 16 O and 13 C 16 O. The E 1 ⌸, vϭ1 state of 12 C 17 O is observed for the first time.

Narrow-band tunable extreme-ultraviolet laser source for lifetime measurements and precision spectroscopy

“…Since the perturber interacts with the f symmetry levels, it is of either ⌺ Ϫ or ⌸ character. A similar example of an accidental predissociation was recently analyzed for the E 1 ⌸, v ϭ 1, J ϭ 7 level of CO, 19 which was attributed to an interaction with the k 3 ⌸ triplet state. That the L 1 ⌸ f state is also slightly perturbed between J ϭ 10 and J ϭ 11 makes this example particularly similar to that of the E 1 ⌸ state, so the perturber state is possibly a 3 ⌸ state as well.…”

“…Laser spectroscopic techniques, involving line-broadening measurements, were developed that improved accuracies to the 10% level. 1,2,4,19 A compilation of predissociation rates and lifetimes, including rotational-state and isotopic dependencies, was recently published. 20 Since the studies of Letzelter et al,17 all excited states of CO in the energy range above 100 000 cm Ϫ1 are considered to be predissociative with a predissociation yield of dis Ͼ 99%.…”

The photodissociation and chemistry of CO isotopologues: applications to interstellar clouds and circumstellar disks

“…Band positions for isotopologues other than 12 CO are still scarce, although many more are currently known from experiments than in 1988. The C1 and E1 bands have been measured for all six natural isotopologues, and the E0 band for all but 13 C 17 O, at an accuracy of 0.003 cm −1 (Cacciani et al 1995;Ubachs et al 2000;Cacciani et al 2001;Cacciani & Ubachs 2004). The positions of the E0 band are especially important because of its key role in the isotope-selective nature of the CO photodissociation (Sect.…”

Oxygen isotope fractionation in the vacuum ultraviolet photodissociation of carbon monoxide: Wavelength, pressure, and temperature dependency

“…A significant number of spectroscopic studies have been carried out in the last century to characterize the molecular parameters of CO to better interpret astronomical observations [2][3][4][5][6][7][8][9][10][11][12][13][14][15] .…”