ORCID Profile
0000-0002-8913-6646
Current Organisations
Australian National University
,
James Cook University
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Publisher: Elsevier BV
Date: 07-1989
Publisher: Elsevier BV
Date: 03-2012
Publisher: American Astronomical Society
Date: 2008
DOI: 10.1086/523696
Publisher: Elsevier BV
Date: 11-2006
Publisher: Elsevier BV
Date: 08-2019
Publisher: Elsevier BV
Date: 12-2008
Publisher: Elsevier BV
Date: 12-1998
Abstract: The intracavity laser spectroscopy (ILS) technique has been shown to be a very sensitive method for observing absorption spectra. By considering quantitative results (line-strengths and pressure broadening coefficients) obtained using the ILS method with a dye laser, the technique has been shown to provide quantitative information that is in excellent agreement with the values afforded by use of more traditional methods for acquiring absorption spectra. A similar investigation has been conducted for an ILS system based on a Ti:sapphire laser. Presented here are quantitative results for water vapor transitions occurring around 795 nm. Line intensities are determined as a function of water vapor pressure and effective path length (i.e., generation time). The line-strengths are compared with values determined by R. A. Toth [J. Mol. Spectrosc. 166, 176-183 (1994)] who used a multipass cell and the Fourier transform spectrometer at the Kitt Peak National Observatory. The good agreement between the results demonstrates that quantitatively accurate data can be obtained using the ILS technique with a Ti:sapphire laser. Copyright 1998 Academic Press.
Publisher: Elsevier BV
Date: 02-2011
Publisher: Elsevier BV
Date: 05-2019
Publisher: Springer Science and Business Media LLC
Date: 1996
DOI: 10.1007/BF00644324
Publisher: AIP Publishing
Date: 09-05-2011
DOI: 10.1063/1.3589862
Abstract: Intracavity laser absorption spectroscopy has been used to record rotationally resolved electronic spectra of Pt2 in the near infrared. The metal dimers were created using a 50 mm-long, platinum-lined hollow cathode plasma discharge. The observed transition at 12 937 cm−1 is identified as the (1,0) band of System VI, with state symmetries Ω = 0 – X Ω = 0.
Publisher: Elsevier BV
Date: 2000
Publisher: Elsevier BV
Date: 03-2017
Publisher: Elsevier BV
Date: 11-2002
Publisher: Elsevier BV
Date: 02-2002
Publisher: Elsevier BV
Date: 03-1995
Publisher: AIP Publishing
Date: 05-09-2019
DOI: 10.1063/1.5113510
Abstract: Several new vibrational bands of the [12.5] Ω = 0+–X3Σ−Ω=0+ and the [15.9] B Ω = 0+–X3Σ−Ω=0+ transitions have been observed in high resolution absorption measurements recorded using Intracavity Laser Spectroscopy (ILS). These new bands have been rotationally analyzed and incorporated into a comprehensive PtS dataset that was fit to a mass-independent Dunham expression using PGOPHER. The comprehensive dataset included all reported field-free, gas phase spectroscopic data for PtS, including 32 Fourier transform microwave transitions (estimated accuracy: 1 kHz), 9 microwave/optical double resonance transitions (25 kHz), 51 millimeter and submillimeter transitions (25–50 kHz), 469 molecular beam-laser induced fluorescence transitions (0.003 cm−1), and 4870 ILS transitions (0.005 cm−1). The determined equilibrium constants have been used with the Rydberg-Klein-Rees method to produce potential energy curves for the four known electronic states of PtS. Isotopic shifts in electronic transition energy beyond expectations from the Born-Oppenheimer approximation were observed and treated as electronic field-shift effects due to the difference in the nuclear charge radius between Pt isotopes. The magnitude and sign of the determined field-shift parameters are rationalized through the analysis of the previously reported ab initio calculations.
Publisher: American Chemical Society (ACS)
Date: 10-1988
DOI: 10.1021/J100331A047
Publisher: Elsevier BV
Date: 2019
Publisher: Elsevier BV
Date: 10-1995
Publisher: AIP Publishing
Date: 05-09-1994
DOI: 10.1063/1.112040
Abstract: Spatially resolved concentrations of excited atomic hydrogen (n=2), generated from 13.56 MHz RF hydrocarbon discharges, are determined during film formation using intracavity laser spectroscopy. Self-bias voltages and pressures of methane (25 and 100 mTorr) and benzene (25 mTorr) are selected so that diamondlike carbon films are deposited. In all cases, the minimum concentration occurs at the power electrode. Benzene produces the least amount of excited atomic hydrogen overall. The results may have implications concerning the proposed impact induced fragmentation of hydrocarbon molecules during film growth.
Publisher: AIP Publishing
Date: 27-08-2014
DOI: 10.1063/1.4893703
Abstract: The (2,0) vibrational band of the A 2Σ− − X 2Π1/2 transition of platinum nitride, PtN, was recorded at Doppler-limited resolution using intracavity laser absorption spectroscopy (ILS) and at sub-Doppler resolution using molecular beam laser induced fluorescence (LIF) spectroscopy. Isotopologue structure for 194PtN, 195PtN, and 196PtN, magnetic hyperfine splitting due to 195Pt (I = ½), and nuclear quadrupole splitting due to 14N (I = 1) were observed in the spectrum. Molecular constants for the ground and excited states are derived. The hyperfine interactions are used to illuminate the nature of the A 2Σ− excited electronic state.
Publisher: Elsevier BV
Date: 09-1994
Publisher: Elsevier BV
Date: 09-2010
Publisher: Elsevier BV
Date: 10-1986
Publisher: Elsevier BV
Date: 07-1994
Publisher: Elsevier BV
Date: 05-2001
Publisher: Optica Publishing Group
Date: 20-06-1997
DOI: 10.1364/AO.36.004062
Abstract: Intracavity laser absorption spectroscopy with ultrahigh sensitivity and enhanced spectral resolution is demonstrated. It entails use of an intracavity étalon that selects equally spaced modes of the cavity. These modes are reduced in intensity when they occur at spectral locations where absorption that is due to intracavity species also occurs. We obtained absorption spectra by tuning the étalon in small steps across its free spectral range, recording intracavity spectra at each step, and summing the result. The maximum resolution is determined by the width of the étalon peaks, which was ~0.01 cm(-1). When the finesse of the étalon is increased, the resolution equal to the width of a single laser mode can be achieved. With this technique, spectra at Doppler-free resolution such as that required for studies of high vibrational-overtone transitions of molecules in supersonic jets are possible.
Publisher: Elsevier BV
Date: 09-1994
Publisher: Elsevier BV
Date: 07-2006
Publisher: Elsevier BV
Date: 10-2013
Publisher: Elsevier BV
Date: 05-2007
Publisher: Elsevier BV
Date: 02-2010
Publisher: Elsevier BV
Date: 06-2004
Publisher: Elsevier BV
Date: 02-2006
Publisher: Elsevier BV
Date: 10-1994
Publisher: Elsevier BV
Date: 04-2015
Publisher: American Astronomical Society
Date: 03-2005
DOI: 10.1086/427279
Publisher: The Royal Society
Date: 14-04-2023
Abstract: How is the massive dimensionality and complexity of the microscopic constituents of the nervous system brought under sufficiently tight control so as to coordinate adaptive behaviour? A powerful means for striking this balance is to poise neurons close to the critical point of a phase transition, at which a small change in neuronal excitability can manifest a nonlinear augmentation in neuronal activity. How the brain could mediate this critical transition is a key open question in neuroscience. Here, I propose that the different arms of the ascending arousal system provide the brain with a erse set of heterogeneous control parameters that can be used to modulate the excitability and receptivity of target neurons—in other words, to act as control parameters for mediating critical neuronal order. Through a series of worked ex les, I demonstrate how the neuromodulatory arousal system can interact with the inherent topological complexity of neuronal subsystems in the brain to mediate complex adaptive behaviour.
Publisher: Elsevier BV
Date: 2002
Publisher: Elsevier BV
Date: 09-2019
Publisher: Elsevier BV
Date: 2011
Publisher: Canadian Science Publishing
Date: 05-2009
DOI: 10.1139/P08-136
Abstract: The (2,0) band of the B 2 Δ 5/2 -X 2 Δ 5/2 transition has been recorded with rotational resolution using intracavity laser absorption spectroscopy. The gas phase NiH molecules were produced in an electric discharge using a nickel hollow cathode in a pure hydrogen atmosphere at 2–3 torr total pressure. Peak positions for the NiH isotopologues are presented for these transitions. Large isotopologue splittings are observed for B 2 Δ 5/2 -X 2 Δ 5/2 (2,0) transitions. A strong perturbation is observed in the excited state at J f′ = 6.5. NiH isotopologue ratios in stellar spectra can be used to determine the neutron to proton ratio, with a view to probing models of supernovae and star formation.
Publisher: Elsevier BV
Date: 02-2009
Publisher: American Chemical Society (ACS)
Date: 26-11-2004
DOI: 10.1021/JP045812M
Publisher: Elsevier BV
Date: 2009
Publisher: AIP Publishing
Date: 04-1989
DOI: 10.1063/1.342747
Abstract: Absorption spectra of the BH2 radical and atomic B are detected by intracavity laser spectroscopy (ILS) in situ during the plasma dissociation of gaseous diborane (B2H6). Rovibronic absorption transitions of BH2 are observed near 15 469 cm−1 [(0,11,0)2B′1 –(0,0,0)2A″1] and 13 605 cm−1 [(0,9,0)2B′1 –(0,0,0)2A″1]. Absorption corresponding to the 3p (2P0)-5s (2S) transitions of atomic B are observed at 11 534.6 and 11 532.8 cm−1. Although atomic B has been detected previously under experimental conditions used in the plasma-assisted preparation of boron-containing films from B2H6, the ILS data presented here establish, for the first time, the presence of BH2 under chemical vapor deposition conditions.
Publisher: AIP Publishing
Date: 28-05-2018
DOI: 10.1063/1.5017958
Abstract: The a 4Σ−–X 2Π1/2 transition of GeH has been recorded in absorption for the first time using Intracavity Laser Spectroscopy (ILS). The GeH molecules were produced in a 0.40–0.60 A DC plasma discharge inside an aluminum hollow cathode, using 500 mTorr of Ar, 100 mTorr of H2, and 200 mTorr of GeH4. This cathode is located within the resonator cavity of a Coherent Verdi™ V-10 pumped dye laser. Effective path lengths for this series of measurements using the ILS method ranged from 2 to 7 km. Spectra were calibrated using the absorption spectrum of I2 collected from an extracavity cell, the I2 transmission spectrum from Salami and Ross, J. Mol. Spectrosc. 223(1), 157 (2005) and PGOPHER’s [C. M. Western, J. Quant. Spectrosc. Radiat. Transfer 186, 221–242 (2016)] calibration feature. Differences in peak positions between calibrated experimental spectra and the reference data were on average less than ±0.002 cm−1. All eight branches expected to have appreciable intensity for the transition have been identified, and isotopologue splitting was observed in features of 5 of the 8 identified rotational branches. Molecular constants have been obtained for the a 4Σ− states of 70GeH (20.84% abundant), 72GeH (27.54% abundant), and 74GeH (36.28% abundant). The transitions were fit using PGOPHER, holding the ground state constants fixed to the values reported by Towle and Brown [Mol. Phys. 78(2), 249 (1993)]. The constants for the a 4Σ− state of 74GeH determined by the fit are T0 = 16 751.5524(13) cm−1, B0 = 6.764 912(33) cm−1, D0 = 0.459 60(17) × 10−3 cm−1, λSS = 9.7453(12) cm−1, λD = 0.468(14) × 10−3 cm−1, γ = 0.077 878(84), and γS = −0.361(77) × 10−3 cm−1.
Publisher: Elsevier BV
Date: 11-2013
Publisher: Elsevier BV
Date: 03-2016
No related grants have been discovered for James O'Brien.