Assignments of methanol laser lines by frequency measurements and Fourier transform spectroscopy

We have measured the frequencies of four CH₃OH far-infrared laser lines that were previously known only by wavelength measurement. Two of these lines turned out to be doublets, bringing the total number of measured lines to six. We can now confirm the assignments of five of them and definitely disprove the assignments proposed for the sixth.In particular we confirm the assignments for the four strong laser lines at 205 and 208 µm pumped by the 9-P(34) CO₂ laser line. These lines share a common upper level in the first excited CO-stretch state, and terminate in the upper and lower levels of a hybrid state with J=5. Heterodyne frequency measurements and conventional microwave spectroscopy show that both lines are split into two components approximately 3.5 MHz apart. The origin of this further splitting is interpreted as a perturbed K-splitting.Work supported by Consiglio Nazionale delle Ricerche -Italia     

Acoustooptic extension of the frequency tunability of CW CO2 lasers: New FIR lasers emissions from CH3OH and13CH3OH

We have increased the frequency tunability of our CW waveguide CO₂ lasers by means of an acoustooptic amplitude modulator, operating at the fixed frequency of 90 MHz. The up-shifted, or down-shifted, laser optical sideband can be generated independently by adjusting the orientation of the modulator. The efficiency is larger than 50%. The frequency tunability of the CO₂ laser around each laser line is thus increased by 180 MHz. To demonstrate the possibilities of this method, a source composed of the above modulator and of a CW, 300 MHz tunable waveguide CO₂ laser has been used for the search of new large offset FIR laser lines from optically pumped CH₃OH and¹³CH₃OH molecules. As a result 15 and 10 new large offset laser lines were discovered respectively. New assignments of some laser lines are also proposed. We have also measured the Stark effect, the offset, and the polarization of other already known lines. In particular a Stark effect frequency tuning of about 1 GHz is demonstrated for a laser line at 208.399 m.     

Applications of high resolution spectroscopy to the identification of far-infrared laser emission from optically pumped13CH3OH

High-resolution infrared (IR) and far infrared (FIR) Fourier transform absorption spectra have been employed to investigate assignments of FIR laser lines reported from optically-pumped¹³CH₃OH. The spectroscopic measurements are used in conjunction with the reported IR pump and FIR laser frequencies to form closed combination loops for several systems, serving to confirm the assignments and in some cases to improve the accuracy of the FIR laser frequencies. Frequency predictions from combination differences are also presented for a number of potential new FIR laser lines.     

The delocalized d-electrons in the semimagnetic alloy Cd1−xMnxTe

The first angular dependent photoemission studies of the semimagnetic semiconductor Cd_1?xMn_xTe are reported. These studies provide no evidence for the commonly assumed presence of a highly localized 3d⁵ ground state, but rather indicate strong hybridization between the Mn⁺⁺ d-levels and the primarily Te-derived valence bands.     

Equilibrium properties of the cubic phases of cobalt

Lattice constants and magnetic moments of face-centered cubic (fcc) and body-centered cubic (bcc) phases of cobalt obtained from self-consistent spin-polarized total-energy calculations by the augmented spherical wave method are compared to measurements. The calculated lattice constants fit the measured values of both phases to about 1%, but favor one of the two reported results on the newly-synthesized bcc phase. However the reported magnetic moments are substantially lower than the theoretical value for the bcc phase. We show that bcc cobalt is metastable up to 400 kbars pressure and, like fcc cobalt, is a strong ferromagnet. The magnetic moment of fcc cobalt is shown to collapse at a 5% lattice compression.     

The atomic structure of alloy surfaces: Ni3Al{001}

The atomic structure of the {001} surface of Ni₃Al has been determined by LEED (low-energy electron diffraction) intensity analysis to correspond to simple truncation of the bulk structure with the Ni-Al mixed layer on top rather than the pure Ni layer. The first interlayer spacing is essentially equal to the bulk interlayer spacing between {001} planes. First-principles calculations of the cohesive energies of slabs terminating in the two types of layers also indicate that the mixed layer termination is more stable.