Methanol as a sensitive probe for spatial and temporal variations of the proton-to-electron mass ratio

The 6.7 and 12.2 GHz masers, corresponding to the 5(1) → 6(0)A+ and 2(0) → 3(-1)E transitions in methanol (CH3OH), respectively, are among the brightest radio objects in the sky. We present calculations for the sensitivity of these and other transitions in the ground state of methanol to a variation of the proton-to-electron mass ratio. We show that the sensitivity is greatly enhanced due to a cancellation of energies associated with the hindered internal rotation and the overall rotation of the molecule. We find sensitivities of K(μ) = -42 and K(μ) = -33, for the 5(1) → 6(0)A+ and 2(0) → 3(-1)E transitions, respectively. The sensitivities of other transitions in the different isotopologues of methanol range from -88 to 330. This makes methanol a sensitive probe for spatial and temporal variations of the proton-to-electron mass ratio.     

Experimental system for research on ultracold atomic gases near superconducting microstructures

We describe an experimental system that integrates the techniques for producing ultracold atomic gases with the techniques for cooling solid bodies to cryogenic temperatures. Ultracold clouds of ⁸⁷Rb are prepared in a trap setup based on room-temperature coils and subsequently transported to a superconducting microstructure by means of optical tweezers. The superconducting microstructure generates a magnetic microtrap and is cooled by a helium-flow cryostat that can achieve temperatures down to 2 K. Both the room-temperature trap setup and the superconducting microtrap are installed in the same ultra-high-vacuum chamber. The presented system is well suited to create hybrid quantum systems by combining ultracold atomic gases and superconducting devices.     

Abelian categories, almost split sequences, and comodules

The following are equivalent for a skeletally small abelian Hom-finite category over a field with enough injectives and each simple object being an epimorphic image of a projective object of finite length.

(a) Each indecomposable injective has a simple subobject.

(b) The category is equivalent to the category of socle-finitely copresented right comodules over a right semiperfect and right cocoherent coalgebra such that each simple right comodule is socle-finitely copresented.

(c) The category has left almost split sequences.

     

Ground and first excited torsional states of acetamide

We present a first global study involving rotational levels in the lowest three torsional states of acetamide (CH₃CONH₂). New measurements of this spectrum, consisting of approximately 1600 lines and involving torsion-rotation transitions with J up to 20 and K_a up to 11, have been carried out between 49 and 149 GHz using the millimeter-wave spectrometer in Kharkov. After removing the observed quadrupole hyperfine splittings, the new data were combined with previously published measurements and fitted using a rho-axis-method (RAM) torsion-rotation Hamiltonian in conjunction with a new computer-automated v_t and K labeling algorithm. The final fit used 48 parameters to give an overall weighted standard deviation of 0.72 for 759, 587, and 265 lines belonging, respectively, to the ground, first, and second excited torsional states and 95 lines corresponding to Δv_t=1 transitions falling in the millimeter wave range. Separate root-mean-square (rms) deviations for the A (25 kHz) and E (27 kHz) species, as well as for the v_t=0 state (26 kHz), v_t=1 (25 kHz), v_t=2 (22 kHz), and Δv_t=1 transitions (35 kHz) indicate a similar quality of the fit for the two symmetry species and for the three torsional states. The RAM Hamiltonian was found to have rather good predictive ability when fits of only v_t=0 (or only v_t=0 and 1) transitions were used to calculate v_t=1 (or v_t=2) lines. In addition, the combination of this Hamiltonian and the computer-automated v_t and K labeling algorithm seems to provide a rather powerful tool for the precise assignment and fitting of torsion-rotation transitions in C_3v internal-rotor molecules with low torsional potential barriers.     

Absolute line intensities in methyl bromide: The 7-μm region

This work deals, for the first time, with the modeling of absolute line intensities in the fundamental ν₂ and ν₅ bands of CH₃⁷⁹Br and CH₃⁸¹Br at 7 μm. For that, four unapodized absorption spectra of CH₃Br (natural abundance, 99% purity, P × L = 0.082 − 0.165 atm × cm, room temperature) were measured in the range 1260-1560 cm⁻¹, at a resolution of 0.002 cm⁻¹ using a Fourier transform spectrometer Bruker IFS 120 HR. For both isotopomers, 313 line intensities were analyzed within the dyad system required to account properly for the strong Coriolis coupling between ν₂ and ν₅. The intensity fit of experimental data led to the determination of the dipole moment derivatives d₂ = ∂μ/∂q₂ and d₅ = ∂μ/∂q₅ relative to the ν₂ and ν₅ bands, as well as the first-order Herman-Wallis correction in K to d₅. The observed line intensities are fitted to 3.0% (3.3%) for ν₂ at 1309.9 cm⁻¹ and 2.6% (3.0%) for ν₅ at 1442.9 cm⁻¹, respectively for CH₃⁷⁹Br and CH₃⁸¹Br. The values derived for the vibrational band strengths of ν₂ and ν₅ are 55.7(0.6) and 39.2(0.3) cm⁻² atm⁻¹ at 296 K, respectively. The corresponding assignments and line positions of the dyad from previous work [F. Kwabia Tchana, I. Kleiner, J. Orphal, N. Lacome, O. Bouba, J. Mol. Spectrosc. 228 (2004) 441] are combined with the present intensity study to provide an improved CH₃Br database for atmospheric applications.     

The preparation and properties of 6-phenylacetamido- and 6-phenoxyacetamidopenicillan-3-acetic acids (“homopenicillins”)

6-Phenylacetamido- and 6-phenoxyacetamidopenicillan-3 -acetic acids (homopenicillins) have been obtained from benzyl- and phenoxymethylpenicillins respectively, via their diazoketones. In these compounds, the carboxyl group is separated from the basic thiazolidine--lactam ring of the penicillins by a methylene group, The homopenicillins, which were characterized as their anilides, possess low antibacterial activity and are powerful penicillinase inducers.