New Proof of the Number of Ways of Forming Noncyclic n-Mers

When every valency in n monomer units is assigned an individual index number, a unique formula can be written for each non-cyclic n-mer by systematically listing the pairs of valencies forming the (n - 1) bonds. The chosen system allows the formulae to be partitioned into families and subfamilies and the number of ways of pairing the valencies in any set to be deduced. This leads to a new method of calculating the number of ways of forming noncyclic n-mers.     

Multi-species detection using multi-mode absorption spectroscopy (MUMAS)

The detection of multiple species using a single laser and single detector employing multi-mode absorption spectroscopy (MUMAS) is reported. An in-house constructed, diode-pumped, Er:Yb:glass micro-laser operating at 1,565 nm with 10 modes separated by 18 GHz was used to record MUMAS signals in a gas mixture containing C₂H₂, N₂O and CO. The components of the mixture were detected simultaneously by identifying multiple transitions in each of the species. By using temperature- and pressure-dependent modelled spectral fits to the data, partial pressures of each species in the mixture were determined with an uncertainty of ±2 %.     

Thermal grating and broadband degenerate four-wave mixing spectroscopy of OH in high-pressure flames

2 ∑–X²Π(0,0) band of OH has been studied in premixed methane/air flames using a cw Ar⁺ laser probe. Measurements of flame temperature and pressure were derived from fits of theoretical simulations to the observed time variation of signals over a pressure range of 10 to 40 bar and for different stoichiometry that were in agreement with independent measurements using N₂ CARS and predictions of a one-dimensional flame calculation. Broadband DFWM spectra in the same band of OH were observed up to a pressure of 9 bar, above which signals were obtained only from scattering from thermal gratings. Received: 10 November 1997/Revised version: 28 May 1998     

Detection of NO in a spark-ignition research engine using degenerate four-wave mixing

We report the first application of degenerate four-wave mixing (DFWM) to combustion diagnostics in a methane-fuelled internal combustion research engine. Combustion-generated NO in the spark-ignited engine was detected using scanning narrowband DFWM in a modified forward folded BOXCARS geometry. The resulting spectra of the X²Π-A²Σ⁺(0,0) band at 226 nm display an excellent signal-to-noise ratio. Extension of the technique to different engine operating conditions and to time-resolved multiplex DFWM is discussed. Received: 3 May 2001 / Revised version: 1 October 2001 / Published online: 29 November 2001     

Multi-mode absorption spectroscopy, MUMAS, using wavelength modulation and cavity enhancement techniques

Multi-mode absorption spectroscopy, MUMAS, has been combined with the techniques of wavelength modulation spectroscopy, WMS, and cavity enhanced absorption spectroscopy, CEAS, to record multiple molecular transitions using a single laser and a single detector. MUMAS signals were recorded using a multi-mode diode laser of the A-band $b^{1}\varSigma _{g}^{+}\leftarrow X^{3}\varSigma _{g}^{-}Multi-mode absorption spectroscopy, MUMAS, has been combined with the techniques of wavelength modulation spectroscopy, WMS, and cavity enhanced absorption spectroscopy, CEAS, to record multiple molecular transitions using a single laser and a single detector. MUMAS signals were recorded using a multi-mode diode laser of the A-band b¹\varSigma _g⁺? X³\varSigma _g^-b^{1}\varSigma _{g}^{+}\leftarrow X^{3}\varSigma _{g}^{-} of molecular oxygen at 760 nm. Direct MUMAS and WMS-MUMAS signals were recorded using a White cell for air and pure oxygen for pressures in the range 0 to 1 bar. CEAS-MUMAS signals were recorded with and without WMS in an open enhancement cavity containing laboratory air. Enhancement of the signal-to-noise ratio has been obtained demonstrating the potential for increased detection sensitivity for gas-sensing applications of MUMAS.     

Multi-mode absorption spectroscopy of oxygen for measurement of concentration, temperature and pressure

The use of multi-mode absorption spectroscopy (MUMAS) to detect multiple transitions in the A-band b¹Σ_g ⁺-X³Σ_g ^- of molecular oxygen is reported. The modelling of MUMAS signatures and the procedure for fitting such model signatures to experimental data obtained using a multi-mode diode laser is described. The technique is shown to allow accurate and precise measurement of concentration, temperature over the range 300 to 500 K and of pressure over the range 0.2 to 1 bar. Extension of the technique to other ranges of temperature and pressure and to other species is discussed. PACS 42.62.Fi; 33.20.Kf     

Pyridine-tert-nitrogen-phenol ligands: N,N,O-Type tripodal chelates for the [M(CO)3]+ core (M = Re, Tc)

The design rationale, synthesis, and preliminary radiolabeling evaluation of new N,N,O-type pyridyl- tert-nitrogen-phenol ligands for the [M(CO) 3] (+) core, where M = (99m)Tc or Re, are described. The capability of the ligands to bind this technetium core is initially demonstrated by using the cold surrogate [Re(CO) 3] (+). NMR studies of the relevant rhenium tricarbonyl complexes indicate the formation of either a monomeric or a possible dimeric complex with each phenolic O atom bridging between two metal centers. Labeling with [ (99m)Tc(CO) 3] (+) provided further insight into the differences in complex formation on the dilute, no carrier added, level compared to the macroscopic scale at which the Re (I) counterparts were made. These new tridentate, monoanionic ligands are competent chelates in binding the [ (99m)Tc(CO) 3] (+) core because radiolabeling yields ranged from 85 to 99% and the resulting complexes were stable to cysteine and histidine challenges for as long as 24 h.     

Thermometry of an oxy-acetylene flame using multiplex degenerate four-wave mixing of C2

Thermometry of an oxy-acetylene flame using multiplex Degenerate Four-Wave Mixing (DFWM) of C₂ is demonstrated. More than 100 rotational transitions in thed ³ _g a ³ _u (0,0) Swan band of C₂ could be recorded simultaneously by use of a pulsed, broad bandwidth modeless laser. Temperatures were inferred by fitting temperature-dependent synthetic spectra of single- or multiple-shot averaged spectra. The strength and reliability of recorded signals together with the large number of rotational lines observed suggest that multiplex DFWM is a promising technique for minor species detection and for temporally resolved temperature measurements in luminous environments. Factors influencing the accuracy and precision of single-shot thermometry using the technique are discussed.