Rotational spectroscopy of methyl tert-butyl ether with a new Ka band chirped-pulse Fourier transform microwave spectrometer.

Chirped-pulse Fourier transform microwave (CP-FTMW) spectroscopy is a powerful tool for performing broadband gas-phase rotational spectroscopy, and its applications include discovery of new molecules, complex mixture analysis, and exploration of fundamental molecular physics. Here we report the development of a new Ka band (26.5-40 GHz) CP-FTMW spectrometer that is equipped with a pulsed supersonic expansion source and a heated reservoir for low-volatility samples. The spectrometer is built around a 150 W traveling wave tube amplifier and has an instantaneous bandwidth that covers the entire Ka band spectral range. To test the performance of the spectrometer, the rotational spectrum of methyl tert-butyl ether (MTBE), a former gasoline additive and environmental pollutant, has been measured for the first time in this spectral range. Over 1000 spectroscopic transitions have been measured and assigned to the vibrational ground state and a newly-identified torsionally excited state; all transitions were fit using the XIAM program to a root-mean-square deviation of 22 kHz. The spectrum displays internal rotation splitting, nominally forbidden transitions, and an intriguing axis-switching effect between the ground and torsionally excited state that is a consequence of MTBE's extreme near-prolate nature. Finally, the sensitivity of the spectrometer enabled detection of all singly-substituted 13C and 18O isotopologues in natural abundance. This set of isotopic spectra allowed for a partial r0 structure involving the heavy atoms to be derived, resolving a structural discrepancy in the literature between previous microwave and electron diffraction measurements.

Coupled Cluster Characterization of 1-, 2-, and 3-Pyrrolyl: Parameters for Vibrational and Rotational Spectroscopy.

Pyrrolyl (C4H4N) is a nitrogen-containing aromatic radical that is a derivative of pyrrole (C4H5N) and is an important intermediate in the combustion of biomass. It is also relevant for chemistry in Titan's atmosphere and may be present in the interstellar medium. The lowest-energy isomer, 1-pyrrolyl, has been involved in many experimental and theoretical studies of the N-H photodissociation of pyrrole, yet it has only been directly spectroscopically detected via electron paramagnetic resonance and through the photoelectron spectrum of the pyrrolide anion, yielding three vibrational frequencies. No direct measurements of 2- or 3-pyrrolyl have been made, and little information is known from theoretical calculations beyond their relative energies. Here, we present an ab initio quantum chemical characterization of the three pyrrolyl isomers at the CCSD(T) level of theory in their ground electronic states, with an emphasis on spectroscopic parameters relevant for vibrational and rotational spectroscopy. Equilibrium geometries were optimized at the CCSD(T)/cc-pwCVTZ level of theory, and the quadratic, cubic, and partial quartic force constants were evaluated at CCSD(T)/ANO0 for analysis using second-order vibrational perturbation theory to obtain harmonic and anharmonic vibrational frequencies. In addition, zero-point-corrected rotational constants, electronic spin-rotation tensors, and nuclear hyperfine tensors are calculated for rotational spectroscopy. Our computed structures and energies agree well with earlier density functional theory calculations, and spectroscopic parameters for 1-pyrrolyl are compared with the limited existing experimental data. Finally, we discuss strategies for detecting these radicals using rotational and vibrational spectroscopy on the basis of the calculated spectroscopic constants.

Rotational Characterization of the Elusive gauche-Isoprene.

Isoprene (2-methyl-1,3-butadiene) is highly abundant in the atmosphere, second only to methane in hydrocarbon emissions. In contrast to the most stable trans rotamer, structural characterization of gauche-isoprene has proven challenging: it is weakly polar, present at the level of only a few percent at room temperature, and structurally complex due to both torsional and methyl tunneling motions. gauche-Isoprene has been observed by two distinct but complementary experimental approaches: chirped-pulse Fourier transform microwave (CP-FTMW) spectroscopy coupled with cryogenic buffer gas cooling, and cavity-enhanced FTMW spectroscopy with a pulsed discharge source. Thermal enhancement of the gauche population (from 1.7% to 10.3%) was observed in the cryogenic buffer gas cell when the sample was preheated from 300 to 450 K, demonstrating that high-energy rotamers can be efficiently isolated under our experimental conditions. Rotational parameters for the inversion states (0+/0-) have been determined for the first time, aided by calculations at increasing levels of theoretical sophistication. From this combined analysis, the inversion splitting Δ E and the Fbc Coriolis coupling constant between the two inversion states have been derived.

From chaos to excellence: preparing for a successful Joint Commission survey.

The new joint Commission on Accreditation of Healthcare Organizations survey requirements make the preparation process more challenging than ever before. In today's competitive healthcare environment, a successful survey is imperative. The authors discuss multiple and innovative ways to prepare for a survey under the 1996 guidelines. Specific examples of processes and forms are included.

Family Medical Leave Act: ready or not!

Many employers already have policies in place that grant job leaves for a variety of reasons. It is no longer optional for employers to grant job leaves; appropriate leave is now the law.

Nerve cells in hydra: monoclonal antibodies identify two lineages with distinct mechanisms for their incorporation into head tissue.

The relationship between populations of nerve cells defined by two monoclonal antibodies was investigated in Hydra oligactis. A population of sensory nerve cells localized in the head (hypostome and tentacles) is identified by the binding of antibody JD1. A second antibody, RC9, binds ganglion cells throughout the animal. When the nerve cell precursors, the interstitial cells, are depleted by treatment with hydroxyurea or nitrogen mustard, the JD1+ nerve cells are lost as epithelial tissue is sloughed at the extremities. In contrast, RC9+ nerve cells remain present in all regions of the animal following treatment with either drug. When such hydra are decapitated to initiate head regeneration, the new head tissue formed is again free of JD1+ sensory cells but does contain RC9+ ganglion cells. Our studies indicate that (1) nerve cells are passively displaced with the epithelial tissue in hydra, (2) JD1+ sensory cells do not arise by the conversion of body column nerve cells that are displaced into the head, whereas RC9+ head nerve cells can originate in the body column, (3) formation of new JD1+ sensory cells requires interstitial cell differentiation. We conclude from these results that the two populations defined by these antibodies are incorporated into the h ad via different developmental pathways and, therefore, constitute distinct nerve cell lineages.

The wandering gallbladder.

An unusual case of a hypermobile gallbladder and liver is presented. The liver and gallbladder, supported only by a long midline falciform ligament, rotated freely from the right to the left upper quadrant. Because of a long gastrohepatic ligament and mesocolon, intermittent volvulus of the stomach and colon were associated findings.