D. C. Hovde

Sub‐Doppler direct infrared laser absorption spectroscopy in fast ion beams: The fluorine hyperfine structure of HF+

We report the development of a new general technique for measuring vibration–rotation spectra of molecular ions with sub‐Doppler resolution and with accurate determination of the mass and number density of the carriers of all spectral features. With this method, called direct laser absorption spectroscopy in fast ion beams (DLASFIB), we have carried out the first observation of direct absorption of photons by ions in a fast ion beam. Hyperfine‐resolved vibration–rotation transitions of HF+ have been measured, and along with optical combination differences and laser magnetic resonance data, have been analyzed to yield the fluorine hyperfine parameters a, b, c and d for both v=0 and v=1 in the X 2Π state. Comparisons with many‐body perturbation theory results are presented.

All-optical vector atomic magnetometer.

We demonstrate an all-optical magnetometer capable of measuring the magnitude and direction of a magnetic field using nonlinear magneto-optical rotation in cesium vapor. Vector capability is added by effective modulation of the field along orthogonal axes and subsequent demodulation of the magnetic-resonance frequency. This modulation is provided by the ac Stark shift induced by circularly polarized laser beams. The sensor exhibits a demonstrated rms noise floor of ∼65  fT/√[Hz] in measurement of the field magnitude and 0.5  mrad/√[Hz] in the field direction; elimination of technical noise would improve these sensitivities to 12  fT/√[Hz] and 10  μrad/√[Hz], respectively. Applications for this all-optical vector magnetometer would include magnetically sensitive fundamental physics experiments, such as the search for a permanent electric dipole moment of the neutron.

Measurement of the rotational spectrum of HF+ by laser magnetic resonance

Rotational transitions in the X 2Π state of the HF+ molecular ion were measured by laser magnetic resonance spectroscopy. Hyperfine splittings from both nuclei were resolved. An analysis of the J = 3/2 → 5/2 transitions in the Ω = 3/2 spin sublevel is presented.

Determination of the dipole moments of molecular ions from the rotational Zeeman effect by tunable far-infrared laser spectroscopy

The details of the first experimental determination of the dipole moment of a molecular ion from the rotational Zeeman effect are presented, along with an assessment of the ultimate accuracy of the technique.

Laser magnetic resonance in supersonic plasmas: The rotational spectrum of SH+

The rotational spectrum of v=0 and v=1 X 3Σ− SH+ was measured by laser magnetic resonance. Rotationally cold (Tr=30 K), vibrationally excited (Tv=3000 K) ions were generated in a corona excited supersonic expansion. The use of this source to identify ion signals is described. Improved molecular parameters were obtained; term values are presented from which astrophysically important transitions may be calculated. Accurate hyperfine parameters for both vibrational levels were determined and the vibrational dependence of the Fermi contact interaction was resolved. The hyperfine parameters agree well with recent many‐body perturbation theory calculations.

A remotely interrogated all-optical Rb-87 magnetometer

Atomic magnetometry was performed at Earth’s magnetic field over a free-space distance of ten meters. Two laser beams aimed at a distant alkali-vapor cell excited and detected the  87Rb magnetic resonance, allowing the magnetic field within the cell to be interrogated remotely. Operated as a driven oscillator, the magnetometer measured the geomagnetic field with ≲3.5 pT precision in a ∼2 s data acquisition; this precision was likely limited by ambient field fluctuations. The sensor was also operated in self-oscillating mode with a 5.3 pT/Hz noise floor. Further optimization will yield a high-bandwidth, fully remote magnetometer with sub-pT sensitivity.

Laser magnetic resonance rotational spectroscopy of the hydrogen halide molecular ions: H35Cl+ and H37Cl+

Abstract Pure rotational spectra of the X2Π vibronic ground states of H35Cl+ and H37Cl+ molecular ions have been measured by far-infrared laser magnetic resonance (LMR). The spectrometer, which contains an intracavity transverse dc discharge, is described in some detail. The theoretical formalism used to analyze the LMR spectra of HF+, HCl+, and HBr+ is presented. The constants B, q, h, b, eQq0, eQq2, g1, and gR were determined from a least-squares regression analysis of the J = 7 2 ← 5 2 and J = 9 2 ← 7 2 transitions in H35Cl+ and H37Cl+. Values obtained for the molecular parameters support a model of HCl+ with the electron density strongly localized on chlorine and with hydrogen exhibiting a substantial positive charge.

Precise measurement of the J=2←1 fine structure interval in N(II) by far‐infrared laser magnetic resonance

Far‐infrared laser magnetic resonance spectroscopy has been used to measure the J=2←1 fine structure intervals in the 3P ground states of singly ionized 14N and 15N atoms. In 14N(II) this separation is 2459.3703(14) GHz, and in 15N(II) it is 2459.3816(19) GHz. The hyperfine constants and gJ factors have been evaluated for both isotopes. Zero field energies for the hyperfine components of the J=2←1 transition in both isotopes are given in an effort to facilitate their observation in interstellar sources. A complete description of the hyperfine and Zeeman Hamiltonian matrix elements for atomic fine structure transitions is given in an LS coupled basis set.

Velocity modulation laser spectroscopy of molecular ions. The hyperfine-resolved rovibrational spectrum of HF+

34 v = 1 ← 0 R branch infrared transitions in the X 2Π state of the HF+ molecular ion have been measured by velocity modulation laser absorption spectroscopy. Fluorine hyperfine structure was resolved for low J transitions. From a weighted fit of all available high resolution data, values were determined for the v = 0 and v = 1 fluorine hyperfine constants (except b(1)), λ-doubling parameters, rotational and centrifugal distortion constants and the vibrational band origin. Molecular expectation values derived from the hyperfine constants are compared to similar quantities for OH and NH-. An analysis is presented for the v = 0 proton hyperfine structure observed previously by laser magnetic resonance.