R.A. Holt

High-resolution study of the B2Σu+−X2Σg+ system of 14N2+ and 15N2+

Abstract The (0, 1) band of the B 2 Σ u + − X 2 Σ g + system of 14 N 2 + and 15 N 2 + has been studied under high resolution using the method of fast-ion-beam laser spectroscopy. Transition wavenumbers have been measured with an absolute accuracy of −1 . We have also applied the laser-rf-laser double resonance method to 15 N 2 + for the first time. The frequencies of hyperfine components of fine-structure rf transitions in 10 rotational levels of the X 2 Σ g + v ″ = 1 state have been measured absolutely to 10 kHz. Because the hyperfine structure was resolved in both the optical and rf transitions, we were able to observe a hyperfine anomaly in the X 2 Σ g + ground state, and changes in the hyperfine splitting of the B 2 Σ u + state and the neighboring A 2 Π u state arising from strong perturbations between them. Many molecular parameters have been measured for the first time or with greatly improved precision.

Measurements of hyperfine structure in 51V II

We have applied fast-ion-beam laser-fluorescence spectroscopy to measure the magnetic dipole hyperfine structure (hfs) constants of 24 even levels and 31 odd levels in 51V II. These are the first published data for hfs in this ion. These results will be very useful for the measurement of stellar photospheric abundances, studies of the history of nucleosynthesis and the testing of models of stellar interiors. The rather large hyperfine splittings in 51V II significantly affect the saturation and width of absorption lines, and this must be taken into account in order to derive accurate abundances and stellar rotation and micro- and macro-turbulence parameters, as well as to help determine if line blending is occurring.

Measurements of isotope shifts and hyperfine structure in Ti II

We have applied fast-ion-beam laser-fluorescence spectroscopy to measure the isotope shifts of 38 transitions in the wavelength range 429–457 nm and the hyperfine structures (hfs) of 22 levels in Ti II. The isotope shift and hfs measurements are the first for these transitions and levels. These atomic data are essential for astrophysical studies of chemical abundances, allowing correction for saturation and the effects of blended lines.