Precision spectroscopy and comprehensive analysis of perturbations in the A¹∏(v= 0) state of¹³C¹⁸O

Abstract

We have reinvestigated the A 1 Π(v = 0) level of 13 C 18 O using new high-resolution spectra obtained via multi-photon laser excitation as well as with synchrotron-based Fourier-transform absorption spectroscopy of the A 1 Π − X 1 Σ + (0, 0), e 3 Σ − − X 1 Σ + (1, 0), d 3 ∆ − X 1 Σ + (4, 0), a 3 Σ + − X 1 Σ + (9, 0), and a 3 Π − X 1 Σ + (11, 0) bands. In addition, Fourier-transform emission spectroscopy in the visible range is performed on the B 1 Σ + − A 1 Π(0, 0) band. Spectra of the B 1 Σ + − X 1 Σ + (0, 0) band are measured in order to tie information from the latter emission data to the level structure of A 1 Π(v = 0). The high pressures in the absorption cell at the synchrotron and the high temperatures in the emission discharge permitted monitoring of high rotational quantum levels in A 1 Π(v = 0) up to J = 43. All information, in total over 900 spectral lines, was included in an effective-Hamiltonian analysis of the A 1 Π(v = 0, J) levels that are directly perturbed by the e 3 Σ − (v = 1), d 3 ∆(v = 4), a 3 Σ + (v = 9), D 1 ∆(v = 0), I 1 Σ − (v = 0, 1) close-lying levels and the e 3 Σ − (v = 0, 2), d 3 ∆(v = 3, 5), a 3 Σ + (v = 8, 10) remote levels, as well being indirectly influenced by the a 3 Π(v = 10, 11) state. The influence of nine further perturber levels and their interactions was investigated and are not significant for reproducing the present experimental data. This analysis leads to a much improved description in terms of molecular constants and interaction parameters, compared to previous studies of the same energy region for other CO isotopologues.

High-resolution Fourier-transform spectroscopy and deperturbation analysis of the A1Π(v = 1) level in 12C18O

“…Vacuum-ultraviolet spectra containing the A 1 18 O were recorded on the DESIRS beamline at the SOLEIL synchrotron. Details of the beamline, spectrometer, and high-temperature absorption cell used to collect the present data, and its reduction to accurate line frequencies are given previously [22,45,[52][53][54] . Briefly, synchrotron radiation is generated by an undulator insertion device with approximately 5 nm spectral bandwidth.…”

“…[38] and isotopic scaling procedure. weak energy level irregularities [19,22,32,45,49,70] (see also Fig. 5 ).…”

“…The rotational operator in the PGOPHER Hamiltonian was taken as a power series expansion in the angular momentum operator excluding spin ( ˆ N ). Definitions of the interaction parameters η and ξ are discussed in [43,45,49] and their relations to α and β perturbation parameters used in Refs. [26,28] are as follows:…”

“…Recently, the A 1 electronic state in 12 C 16 O was accurately re-examined using two experimental techniques: twophoton Doppler-free laser spectroscopy with 0.002 cm −1 accuracy and synchrotron based Fourier-transform (VUV-FT) spectroscopy with an accuracy as good as 0.01 cm −1 [40,41] . Deperturbation analyses of the A 1 state in other isotopologues have been conducted as well: Niu et al [42] for 13 C 16 O A( v = 0), Hakalla et al [43] for 12 C 17 O A( v = 1 -5), Hakalla et al [44] for 13 C 17 O A( v = 0 -3) and Hakalla et al [45] for 13 C 18 O A( v = 0). These analyses were carried out on the basis of experimental spectra obtained by three complementary techniques: FT emission spectroscopy in the VIS range with an accuracy of about 0.005 cm −1 , VUV-FT absorption spectroscopy based on synchrotron radiation with accuracy of about 0.02 cm −1 and two-photon Doppler-free laser spectroscopy with accuracy up to 0.003 cm −1 .…”