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Rotational transitions in the x 2 rr state of the HF+ molecular ion were measured by laser magnetic resonance spectroscopy. Hyperfine sp1ittings from both nuclei were resolved. An analysis of the J =·3/2 + 5/2 transitions in the ~ = 3/2 spin sublevel is presented. we can rigorously assess the reliability of this new direct-sum method.Finally, despite the low cosmic abundance of fluorine, one model of the interstellar medium cites HF+ as a possible interstellar maser;9 accurate rest frequencies obtained from these laboratory measurements will permit an astronomical search. In this article we report the first detection and a preliminary analysis of rotational transitions in HF+, with resolution of both F and H hyperfine splitting. Previous papers 2 ,3 describe the details of our LMR spectrometer.Briefly, it consists of a IS-inch electromagnet and an optically pumped far-infrared laser. A beam splitter separates the intracavity sample cell from the laser gain region, and can be rotated to select either a or TI polarization of the laser electric field relative to the magnetic field.The vacuum for the sample region is provided by a Roots pump (Leybold-Heraus ~vA-2S0,4600 l/min) backed by a mechanical pump (Welch l396F, 2800 l/min).The HF+ was produced in the sample region by a 10 rnA A.C. discharge rms through helium containing a trace of hydrogen fluoride. laser lines, the J = 1/2 ~ 3/2, ~ = 1/2 rotational transition was measured. 3Laser frequencies and magnetic field strengths are presented in Table 1.Chemical and spectroscopic evidence forms the basis for assigning the spectra + to HF. The LMR signals all depend in the same way on the amount of HF added to the discharge, and can not be duplicated using HC1 instead; the peaks disappear when the HF is shut off or increased above 2 Pa (15 mTorr).Unpurified HF, which is contaminated by HZ as noted above, produces weak signals. basis set, and appropriate for a molecule with one nuclear spin. ThisHamiltonian has been incorporated into a computer program capable of including both zero field and magnetic resonance spectra in a single weighted least squares fit. Because the program currently is limited to one nuclear spin, the hydrogen hyperfine structure was averaged out and only the much larger fluorine hyperfine pattern was included in this preliminary analysis. The results of the eight parameter fit using both LMR data and combination differences from the emission spectrum l are presented in Table 2.

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We investigate the effect of plasmon-phonon coupling on the spectrum of laser light scattered by doped semiconductors under high-excitation conditions. A model consisting of the plasmon and LO-phonon subsystems in conditions of quasiequilibrium, characterized by uniform internal temperatures, is used. The scattering cross section is derived through an appropriate generalization of the fluctuation-dissipation theorem and the use of Bogoliubov's Green's-function formalism. The Coulomb interaction between electrons is treated within the random-phase approximation and the Frohlich Hamiltonian is used to describe the electronphonon interaction. The phonon lifetime and plasma lifetime, other than Landau damping, are introduced in a phenomenological way. Numerical calculations for the case of a nondegenerate conduction-electron gas in GaAs are presented. The analysis is completed with a discussion of resonant Raman scattering when "hot" electrons are considered for the intermediate states of the scattering amplitude.