A solid state pulsed NMR spectrometer

A 10 MHz pulsed NMR spectrometer, built using mostly solid state devices, is described. The pulse programmer provides 2-pulse, 3-pulse, saturation burst and Carr-Purcell sequences both in repetitive and manual modes of operation. The transmitter has a maximum power output of ∼ 2 kW with a 75 Ω output impedance termination. The total gain of the receiver system is around 120 dB with a minimum band width of 2 MHz. The recovery time of the receiver is ∼ 7 µsec. A two-channel boxcar integrator capable of working in the single channel, differential and double boxcar modes provides signal to noise ratio improvement. The sensitivity and the linearity of the boxcar integrator are ∼ 2 mV and ∼ 0.1% respectively.

Electron-Energy Loss Spectroscopy (Eels) Of Organic-Molecules In Vapor-Phase - Design And Fabrication Of An Indigenous Eel Spectrometer

An indigenous electron energy loss spectrometer has been designed and fabricated for the study of free molecules. The spectrometer enables the recording of low-resolution electronic spectra of molecules inthe vapour phase with ready access to the vacuum ultraviolet region. Electron energy loss spectra of aliphatic alcohols and carbonyl compounds as wellas of benzene derivatives have been recorded with the indigenous spectrometer and the electronic transitions in these molecules discussed.

A pulsed field gradient spin echo NMR spectrometer for diffusion coefficient measurements

A pulsed field gradient spin echo NMR spectrometer has been assembled by interfacing a programmable pulse generator and a data acquisition system designed and fabricated in our laboratory with other imported units. Calibration results of the magnetic field gradients are presented.

Design and fabrication of an indigenous molecular beam ultraviolet photoelectron spectrometer

An ultraviolet photoelectron spectrometer for the study of van der Waals molecules has been designed and fabricated indigenously. The spectrometer consists of an HeI discharge lamp, a molecular beam sample inlet system, an electrostatic lens, a 180-degrees hemispherical electrostatic analyser and a channeltron detector. Performance of the spectrometer is illustrated with an example.

An electron spectroscopic study of the adsorption of nitrogen on a Ni/TiO2 catalyst prepared in situ in the spectrometer: evidence for dissociative adsorption in the strong-metal-support-interaction (SMSI) state

Nitrogen is dissociatively adsorbed on an annealed Ni/TiO2 surface just as on a Ti–Ni alloy surface while it is molecularly adsorbed on a Ni/Al2O3 surface.

Towards a broadband chirped pulse Fourier transform microwave spectrometer

This article gives a brief review of microwave spectroscopy and the experimental techniques used for obtaining microwave spectrum of molecules and complexes since 1950s. It presents a brief summary of the pulsed nozzle Fourier transform microwave (PNFTMW) spectrometer, fabricated in our laboratory, and discusses some of the important results obtained using the spectrometer. The most significant among the results from this spectrometer is the direct structural determination of weakly bound complexes involving H2O/H2S. These have challenged the conventional wisdom on hydrogen bonding leading us to propose a modern definition for the same through IUPAC. The limitations of the PNFTMW spectrometer and the need for the new chirped pulse Fourier transform microwave spectrometer are discussed as well. Moreover, preliminary results from our laboratory on generating a 1 A mu s chirped pulse of 1 GHz bandwidth are given.

Precision and long-term stability of clumped-isotope analysis of CO2 using a small-sector isotope ratio mass spectrometer

RATIONALE The ratio of the measured abundance of 13C18O bonding CO2 to its stochastic abundance, prescribed by the delta 13C and delta 18O values from a carbonate mineral, is sensitive to its growth temperature. Recently, clumped-isotope thermometry, which uses this ratio, has been adopted as a new tool to elucidate paleotemperatures quantitatively. METHODS Clumped isotopes in CO2 were measured with a small-sector isotope ratio mass spectrometer. CO2 samples digested from several kinds of calcium carbonates by phosphoric acid at 25 degrees C were purified using both cryogenic and gas-chromatographic separations, and their isotopic composition (delta 13C, delta 18O, Delta 47, Delta 48 and Delta 49 values) were then determined using a dual-inlet Delta XP mass spectrometer. RESULTS The internal precisions of the single gas Delta 47 measurements were 0.005 and 0.02 parts per thousand (1 SE) for the optimum and the routine analytical conditions, respectively, which are comparable with those obtained using a MAT 253 mass spectrometer. The long-term variations in the Delta 47 values for the in-house working standard and the heated CO2 gases since 2007 were close to the routine, single gas uncertainty while showing seasonal-like periodicities with a decreasing trend. Unlike the MAT 253, the Delta XP did not show any significant relationship between the Delta 47 and delta 47 values. CONCLUSIONS The Delta XP gave results that were approximately as precise as those of the MAT 253 for clumped-isotope analysis. The temporal stability of the Delta XP seemed to be lower, although an advantage of the Delta XP was that no dependency of delta 47 on Delta 47 was found. Copyright (c) 2012 John Wiley & Sons, Ltd.

Solute induced liquid crystalline behaviour of a quaternary ammonium salt and its application to structure determination

A new liquid crystalline phase, induced by the addition of small amounts of a non-mesogenic solute (such as dimethyl sulphoxide or methyl iodide) to a quaternary ammonium salt, N-methyl-N,N,N-trioctadecylammonium iodide (MTAI), has been detected by NMR and optical microscopic studies. In some cases, there is a coexistence of nematic and smectic phases. Information on the ordering of the phases in the magnetic field of the spectrometer has been derived from NMR spectra of a dissolved molecule, C-13-enriched methyl iodide. The low order parameter of the pure thermotropic nematic phase of the salt provides first-order spectra of the dissolved oriented molecules. Analyses of spectra of cis,cis-mucononitrile exemplifies the utility of the MTAI nematic phase in the determination of structural parameters of the solute.

Co-2-Ions In A Low-Pressure Glow-Discharge Of Carbon-Dioxide

$CO_2^{-}$ ions have been detected in the gas phase and measured by a mass spectrometer with a flight time of 30 µs in the positive column of carbondioxide glow discharge.

05-ions in a low pressure glow discharge of oxygen

0:- ions have been detected and measured in a positive column of glow discharge in oxygen between 0.04 and 0.17 Torr. A suitable ion-molecule reaction has been proposed, which appears to be supported by the mass spectrometer measurements.

Propagating waves in polar coronal holes as seen by SUMER and EIS

Context. To study the dynamics of coronal holes and the role of waves in the acceleration of the solar wind, spectral observations were performed over polar coronal hole regions with the SUMER spectrometer on SoHO and the EIS spectrometer on Hinode. Aims. Using these observations, we aim to detect the presence of propagating waves in the corona and to study their properties. Methods. The observations analysed here consist of SUMER spectra of the Ne VIII 770 angstrom line (T = 0.6 MK) and EIS slot images in the Fe XII 195 angstrom line (T = 1.3 MK). Using the wavelet technique, we study line radiance oscillations at different heights from the limb in the polar coronal hole regions. Results. We detect the presence of long period oscillations with periods of 10 to 30 min in polar coronal holes. The oscillations have an amplitude of a few percent in radiance and are not detectable in line-of-sight velocity. From the time distance maps we find evidence for propagating velocities from 75 km s(-1) (Ne VIII) to 125 km s(-1)(Fe XII). These velocities are subsonic and roughly in the same ratio as the respective sound speeds. Conclusions. We interpret the observed propagating oscillations in terms of slow magneto-acoustic waves. These waves can be important for the acceleration of the fast solar wind.