S. D. Rosner

Fine and hyperfine structure in 14N2

Abstract The fine and hyperfine structure of 14 N 2 + has been observed in 31 rotational lines of the (0, 1) band of the B 2 Σ u + - X 2 Σ g + system using the method of Doppler-tuned laser-induced fluorescence on a molecular ion beam. The spin-rotation constants (γ′, γ″, γ ′ J ) are in good agreement with other experiments in which the hyperfine structure was not resolved. The Fermi-contact ( b ′ F , b ″ F ) and dipolar ( t ′, t ″) hyperfine coupling constants are in reasonably good agreement with values calculated from ab initio wavefunctions. The least-squares experimental values in MHz are γ ″ = 279.1(6), γ ′ = 726.4(6), γ ′ J = −0.0460(2), b ″ F = 105(4), b ′ F = 708(3), t ″ = 49(6), and t ′ = 26(5).

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.

New laser‐induced fluorescence method for molecular beam velocity analysis

We have measured the velocity distribution of a Na2 supersonic beam by a time of flight method in which a chopped beam from an argon ion laser depopulates a single vibration–rotation level of the Na2 ground electronic state, and a continuous laser beam further downstream is used to detect the arrival of the tagged molecules by observation of changes in the laser‐induced fluorescence.

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.

Metastable ion source

A very low‐pressure magnetically‐focused electron bombardment ion source is described which produces substantial quantities of ions in highly excited metastable states. Using the laser–fluorescence technique, we have measured a 2s3S1 metastable content of 0.6%–2.3% in a 0.4 μA, 5 keV beam of 7Li+. The source design can be applied to essentially any ionic species and offers the additional advantage of relatively low energy spread.

Laser-Induced Coherence Effects in Molecular Beam Optical-RF Double Resonance

Optical pumping, from its earliest days, has been used with rf magnetic or electric resonance to make precise measurements of atomic and molecular fine structure, hyperfine structure (hfs), and g-factors [1]. Many such experiments have been performed in cells, where the molecules interact simultaneously with the light, the rf field, the walls, a buffer gas, each other, and in some cases free electrons. The resulting alteration of the rf resonance line profile must be accounted for in extracting the constants appropriate to an isolated molecule.