W. J. Childs

Electric‐dipole moment of CaF (X 2Σ+) by molecular beam, laser‐rf, double‐resonance study of Stark splittings

The molecular beam, laser‐rf, double‐resonance technique has been used to measure the electric‐dipole moment of the X 2Σ+ (v=0) electronic ground state of CaF. The moment was determined to be 3.07(7) D by measuring the Stark shifts of rf transitions within specified rovibrational states of X 2Σ+.

Fine and magnetic hyperfine structure in the A 2Π and X 2∑+ states of yttrium monoxide

A molecular beam optical and rf–optical double resonance spectroscopic study of numerous vibrational components in the A2Π3/2–X2∑+ subband of gas phase YO has been performed. The fine and magnetic hyperfine parameters for v=0–4 of the X2∑+ state have been determined. The observed strong vibrational dependence of the spin–rotation parameter γ(X2∑+) is proposed to arise from a perturbation from two as yet unobserved low‐lying 2Π states coming from a three open‐shell configuration. The magnetic hyperfine parameters for the X2∑+ state can be interpreted in terms of a single unpaired electron model. An estimate for the A2Π excited state dipolar parameter has been established.

A molecular‐beam‐optical and radio frequency‐optical double‐resonance study of the A 2Πr–X 2Σ+ band system of scandium monoxide

A molecular‐beam‐optical and rf‐optical double‐resonance study of the A 2 Π (v’=0–2) –X 2Σ+ (v‘=0–2) band systems of gas phase scandium monoxide has been performed. No localized perturbations in the X 2Σ+ state have been observed but strong perturbations in the A 2 Πr (v=1) state were detected. Quantum numbers for the optical spectrum could only be assigned assuming a negative value for the excited state Λ‐doubling‐type magnetic hyperfine parameter, contrary to current theoretical understanding of this interaction. The ground state magnetic hyperfine parameters can be interpreted in terms of ab initio models for the electronic states of ScO whereas the spin‐rotation parameters cannot.

Hyperfine structure of the X 2Σ+ ground state of Ca 35Cl and Ca 37Cl by molecular‐beam, laser‐rf double resonance

The hyperfine structure of the X 2Σ+ state of Ca 35Cl and Ca 37Cl, unresolved in previous studies, has been investigated in detail by the molecular‐beam, laser‐rf, double‐resonance technique. Results for the spin‐rotation interaction and the dipole and quadrupole hfs constants are given in the form of Dunham coefficients so that the N\ and v\ dependence of each constant can be explicitly exhibited. The results, after dividing out the purely nuclear effects, fall between the corresponding values for CaF and CaBr, as expected.

High-precision measurement of 235 U ground-state hyperfine structure by laser-rf double resonance

The laser-rf double-resonance technique has been used to make precise (±1-kHz) measurements of four hyperfine intervals in the atomic ground state of 235U. It is found that A = −60.559 ± 0.003 MHz and B = 4104.15 ± 0.20 MHz, uncorrected for second-order effects.

New line classifications in Ho i based on high-precision hyperfine-structure measurement of low levels

Doppler-free laser-fluorescence and laser-rf double-resonance studies have been made of the hyperfine structure (hfs) of four strong, previously unclassified visible lines in Ho i; all are shown to connect with low levels. The hfs of the 4f116s24I11/2,9/2 levels is measured in detail, allowing evaluation of the dipole (a01, a12, a10) and quadrupole (b02, b11, b13) hfs radial integrals. The results are in close agreement with the ab initio values of Lindgren Rosen [ Case Stud. Atom. Phys.4, 93– 292 ( 1974)]. The value found for b02 in the 4f116s2 configuration is in reasonable agreement with that of Wyart Camus [ Physica93C, 227– 236 ( 1978)], thereby confirming their finding of a substantial dependence of this parameter on the number of 4f electrons in the core.

High-precision laser and rf spectroscopy of the spin-rotation and hfs interactions in the X2Σ+ and B2Σ+ states of LaO

Abstract The spin-rotation and hyperfine interactions in the X2Σ+ and B2Σ+ electronic states of 139La16O have been studied using Doppler-free laser-induced fluorescence and molecular-beam laser-rf double resonance. Observations were made for several values of v and many values of N, allowing evaluation of the principal interaction strengths and their N and v dependences for both the X and B states. The results are compared with earlier results for the isoelectronic system 137Ba19F.

Spin–rotation and hyperfine structure in the X 2Σ+ state of yttrium monosulfide by molecular‐beam laser‐radio‐frequency double resonance

The molecular‐beam laser‐radio‐frequency double‐resonance method has been used to measure the spin–rotation and magnetic hyperfine structure of yttrium monosulfide (YS) in its X 2Σ+ electronic ground state. The spin–rotation constant γ is found to be positive, unlike that of YO. The Fermi contact and dipolar hyperfine interactions (due to the spin I=1/2 of 89Y) are found to be rather close to the corresponding quantities in YO. The contact hfs constant b in the excited B 2Σ+ state of YS was determined by combining the directly measured X 2Σ+ splitting information with B–X optical hfs observations.

The fine and magnetic hyperfine structure of 87SrF in its X 2Σ+ state

A molecular beam rf–optical double resonance experiment was performed on 87SrF in its naturally occurring abundance ratio. The natural occurring abundances of the strontium isotopes are 86Sr (9.8%), 87Sr(7.02%) and 88Sr (82.5%). Numerous magnetic dipole allowed transitions between ρ‐doublets in the X 2Σ+ state were measured to an accuracy of 3 kHz. The observed spectra were analyzed in terms of an effective Hamiltonian which includes the magnetic hyperfine and electric quadrupole interactions arising from the 87 Sr (I=9/2) and 19F (I=1/2) nuclei. The extracted spectroscopic hyperfine parameters were interpreted in terms of a simple molecular orbital picture for the electronic nature of the X 2Σ+ state. A comparison is made to previous results for the more abundant 86SrF and 88SrF isotopic forms.

Hyperfine structure of 4ƒ^N 6s^2 configurations in ^159Tb, ^161,163Dy, and ^169Tm

The atomic-beam, laser-rf, double-resonance method has been used to measure the hyperfine structure in excited levels of the 4ƒN 6s2 configurations of the neutral rare earths 159Tb, 161,163Dy, and 169Tm. On combining the new information with earlier results for the lower levels, it is possible to extract many of the hyperfine radial integrals (〈r−3〉xy). The present results, together with work published during the last year on 165Ho and 167Er, now make it possible to plot the values of the integrals completely across the 4ƒ shell. The ab initio calculations of Lindgren and Rośen reproduce the magnetic-dipole hfs integrals well but appear to overestimate the electric-quadrupole integrals 〈r−3〉11 and 〈r−3〉13.