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The hydrogen bonds involving sulfur in the furfuryl mercaptan monohydrate are compared with the interactions originating from the hydroxyl group in furfuryl alcohol. The dimers with water were created in a supersonic jet expansion and characterized using microwave spectroscopy and supporting molecular orbital calculations. In furfuryl alcohol-water, a single isomer is observed, in which the water molecule forms an insertion complex with two simultaneous hydrogen bonds to the alcohol (O-H⋅⋅⋅O ) and the ring oxygen (O -H⋅⋅⋅O ). When the alcohol is replaced by a thiol group in furfuryl mercaptan-water, two isomers are observed, with the thiol group preferentially behaving as proton donor to water. The first isomer is topologically equivalent to the alcohol analog but the stronger hydrogen bond is now established by water and the ring oxygen, assisted by a thiol S-H⋅⋅⋅O hydrogen bond. In the second isomer the sulfur group accepts a proton from water, forming a O -H⋅⋅⋅S hydrogen bond. Binding energies for the mercaptan-water dimer are predicted around 12 kJ mol weaker than in the alcohol hydrate (B3LYP-D3(BJ)). The non-covalent interactions in the furfuryl dimers are dominantly electrostatic according to a SAPT(0) energy decomposition, but with increasing dispersion components in the mercaptan dimers, which are larger for the isomer with the weaker O -H⋅⋅⋅S interaction.

The spectrum of Zr III has been observed in the chemically peculiar B-type star Chi Lupi with the Goddard high-resolution spectrograph on the Hubble space telescope. Oscillator strengths for the dipole-allowed fine-structure transitions in Zr III between the levels belonging to the 4d2 and 4dnl (n = 4-6 and l = 1-3) configurations, which may be useful for abundance determinations, have been calculated in the LSJ-coupling scheme using the relativistic quantum-defect orbital method, with and without explicit account for core-valence correlation. For some of the studied fine-structure transitions the presently calculated f-values are the only ones available in the literature.

Abstract. Oscillator strengths for 3s2 3p 2 → 3s 2 3p 1 3d 1 and 3s 2 3p 2 → 3s 2 3p 1 4s 1 transitions in the silicon sequence (KVI -XeXLI) have been calculated using the Relativistic Quantum Defect Orbital (RQDO) method, with and without explicit inclusion of core-valence correlation, and the multiconfigurational Dirac-Fock (MCDF) approach. Our f -values, which are of interest in astrophysics and fusion plasma research, are compared with other theoretical results in the cases for which these are available.

Abstract. Relativistic Quantum Defect Orbital (RQDO) calculations of transition probabilities for E2 and M1 forbidden transition in the potassium sequence have been performed. Intensities for the higher ions are reported, to our knowledge, for the first time, as they are potentially important for the study of the plasma in astrophysical objects and fusion devices.

Relativistic quantum defect orbital (RQDO) calculations have been performed with and without taking explicit account of the core-valence correlation of oscillator strengths for the dipole-allowed fine-structure 3p 3 4 S o -3p 2 ( 3 P)3d 4 P transition array of a number of P-like ions (Cl III-La XLIII). The present f -values are analysed on the basis of other theoretical data available in the literature. Regularities in the transition intensities along the isoelectronic sequence for each line of the multiplet are also tested.

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