Cyril Richard

Room-Temperature Metal-Hydride Discharge Source, with Observations on NiH and FeH

A metal sputtering source suitable for laboratory production of metal hydrides is described. Sputtering from pure nickel or iron in an Ar/H(2) discharge is analyzed at low resolution. High resolution laser excitation and dispersed fluorescence spectra of NiH have also been recorded. The source has been designed to operate with a ferromagnetic circuit for Zeeman spectroscopy. Signals from the source are strong enough to record dispersed fluorescence from NiH by Fourier transform interferometry in magnetic fields up to 1 T. We establish that FeH can also be formed in this source.

New investigation of the ν3 C–H stretching region of 12CH4 through the analysis of high temperature infrared emission spectra

The ν3 C-H stretching region of methane was reinvestigated in this work using high temperature (620-1715 K) emission spectra recorded in Rennes at Doppler limited resolution. This work follows our recent global analysis of the Dyad system Δn = ±1 (1000-1500 cm-1), with n being the polyad number [B. Amyay et al., J. Chem. Phys. 144, 24312 (2016)]. Thanks to the high temperature, new assignments of vibration-rotation methane line positions have been achieved successfully in the Pentad system and some associated hot bands (Δn = ±2) observed in the spectral region 2600-3300 cm-1. In particular, rotational assignments in the cold band [Pentad-ground state (GS)] and in the first related hot band (Octad-Dyad) were extended up to J = 30 and 27, respectively. In addition, 1525 new transitions belonging to the Tetradecad-Pentad hot band system were assigned for the first time, up to J = 20. The effective global model used to deal with the new assignments was developed to the 6th order for the first three polyads (Monad, Dyad, and Pentad), and to the 5th order for both the Octad and the Tetradecad. 1306 effective parameters were fitted with a dimensionless standard deviation σ = 2.64. The root mean square deviations dRMS obtained are 4.18 × 10-3 cm-1 for the Pentad-GS cold band, 2.48 × 10-3 cm-1 for the Octad-Dyad, and 1.43 × 10-3 cm-1 for the Tetradecad-Pentad hot bands.

Resolved fluorescence spectra of NiH. Electronic structure, electronic energy transfer, and the Zeeman effect in low-lying states

Fourier transform spectra of collisionally induced fluorescence following isotopically selective laser excitation of NiH at ∼550 nm have located an excited Ω = 1/2 state of NiH lying 17900 cm−1 above the electronic ground state. This is identified as v = 0 of a 2Π1/2 state originating from an Ni+ 3d84s1 2F configuration. Emission from this Ω′ = 1/2 state occurs predominantly to v″ = 0 and 1 of the 2Σ+ and W2 2Π1/2 ligand field states, locating elusive f parity levels of W2 2Π1/2 up to 5600 cm−1 above the first rotational level of the electronic ground state, X 1 2Δ5/2. Collisionally induced fluorescence following laser excitation at lower energies has also been recorded in the presence of a magnetic field (0.7–1 T), at Doppler limited resolution. Effective Landé factors g J for rotational levels of the v = 0 and 1 levels of the low-lying Ω″ = 5/2 and 3/2 components of the 2Δ and 2Π states of NiH have been derived from partially resolved Zeeman patterns. About 1600 transitions recorded in field-free conditions have been reduced to term energies relative to the lowest level of the ground state. They confirm strong spin-orbit mixing between the low-lying ligand-field states.