An accurate line list, called XABC, is computed for nitric oxide which covers its pure rotational, vibrational and rovibronic spectra. A mixture of empirical and theoretical electronic transition dipole moments are used for the final calculation of 14N16O rovibronic A 2Σ+ – X 2Π, B 2Π – X2Π and C 2Π – X 2Π which correspond to the γ, β and δ band systems, respectively, as well as minor improvements to transitions within the X 2Π ground state. The work is a major update of the ExoMol NOname line list. It provides a high-accuracy NO ultraviolet line list covering the complicated regions where the B 2Π-C 2Π states interact. XABC provides comprehensive data for the lowest four doublet states of NO in the region of λ > 160 nm ($\tilde{\nu } < 63~000~\mathrm{cm}^{-1}$) for the analysis of atmospheric NO on Earth, Venus or Mars, other astronomical observations and applications. The data is available via www.exomol.com.

The rovibronic structure of A 2 Σ + , B 2 Π, and C 2 Π states of nitric oxide (NO) is studied with the aim of producing comprehensive line lists for its near ultraviolet spectrum. Empirical energy levels for the three electronic states are determined using a combination of the empirical measured active rotation-vibration energy level (MARVEL) procedure and ab initio calculations, and the available experimental data are critically evaluated. Ab initio methods that deal simultaneously with the Rydberg-like A 2 Σ + and C 2 Π and the valence B 2 Π state are tested. Methods of modeling the sharp avoided crossing between the B 2 Π and C 2 Π states are tested. A rovibronic Hamiltonian matrix is constructed using the variational nuclear motion program DUO whose eigenvalues are fitted to the MARVEL. The matrix also includes coupling terms obtained from the refinement of the ab initio potential energy and spin-orbit coupling curves. Calculated and observed energy levels agree well with each other, validating the applicability of our method and providing a useful model for this open shell system.

A new silicon monoxide (28Si16O) line list covering infrared, visible and ultraviolet regions called SiOUVenIR is presented. This line list extends the infrared EBJT ExoMol line list by including vibronic transitions to the A 1Π and E 1Σ+ electronic states. Strong perturbations to the A 1Π band system are accurately modelled through the treatment of 6 dark electronic states: C 1Σ−, D 1Δ, a 3Σ+, b 3Π, e 3Σ− and d 3Δ. Along with the X 1Σ+ ground state, these 9 electronic states were used to build a comprehensive spectroscopic model of SiO using a combination of empirical and ab initio curves, including the potential energy (PE), spin-orbit (SO), electronic angular momentum (EAM) and (transition) dipole moment curves. The ab initio PE and coupling curves, computed at the multireference configuration interaction (MRCI) level of theory, were refined by fitting their analytical representations to 2617 experimentally derived SiO energy levels determined from 97 vibronic bands belonging to the X–X, E–X and A–X electronic systems through the MARVEL procedure. 112 observed forbidden transitions from the C–X, D–X, e–X, and d–X bands were assigned using our predictions, and these could be fed back into the MARVEL procedure. The SiOUVenIR line list was computed using published ab initio transition dipole moments for the E–X and A–X bands; the line list is suitable for temperatures up to 10 000 K and for wavelengths longer than 140 nm. SiOUVenIR is available from www.exomol.com and the CDS database.

Received XX Month XXXX; revised XX Month, XXXX; accepted XX Month XXXX; posted XX Month XXXX (Doc. ID XXXXX); published XX Month XXXX We propose a method to reconstruct the two-dimensional (2D) velocity distribution of flow fields by laser absorption spectroscopy tomography. A mathematic model is established to reveal the dependence of spectral absorbance on line-of-sight velocity distribution. Then, with multiple laser beams from different angular views covering the region of interest, a nonlinear equation set of 2D velocity distribution is established according to the model. The integrated absorbance coefficient distribution is reconstructed using the Landweber iteration algorithm and substituted into the nonlinear equation set for further simplification. Finally, the velocity distribution is reconstructed by solving the simplified equation group via the interior-point algorithm. The proposed method is validated numerically by reconstructing the velocity distribution of water molecules, as calculated by Computational Fluid Dynamics, over a cross-section of a double-mode scramjet combustor. The method does not require adding extra tracer particles and avoids issues arising from the short lifetime of molecular tags. It is suitable for diagnosis of high-speed flow fields.

A variational model for the infra-red spectrum of VO is presented which aims to accurately predict the hyperfine structure within the VO $\mathrm{X}\,^4\Sigma^-$ electronic ground state.To give the correct electron spin splitting of the $\mathrm{X}\,^4\Sigma^-$ state,electron spin dipolar interaction within the ground state and the spin-orbit coupling between $\mathrm{X}\,^4\Sigma^-$ and two excited states, $\mathrm{A}\,^4\Pi$ and $\mathrm{1}\,^2\Sigma^+$, arecalculated \abinitio alongside hyperfine interaction terms.Four hyperfine coupling terms are explicitly considered:Fermi-contact interaction,electron spin-nuclear spin dipolar interaction,nuclear spin-rotation interaction andnuclear electric quadrupole interaction. These terms are included as part of a fullvariational solution of the nuclear-motion Schr\"odinger equation performed using program \textsc{Duo}, which is used to generate both hyperfine-resolved energy levels and spectra.To improve the accuracy of the model, \abinitio curves are subject to small shifts.The energy levels generated by this modelshow good agreement with the recently derived empirical term values.This and other comparisonsvalidate both our model and the recently developed hyperfine modules in \textsc{Duo}.