B. Simard - Academia.edu (original) (raw)

Papers by B. Simard

Research paper thumbnail of Rotational, fine, and hyperfine analyses of the (0,0) band of the D 3Π–X 3Δ system of vanadium mononitride

The Journal of Chemical Physics, 1993

ABSTRACT

Research paper thumbnail of Tilted fiber Bragg grating assisted nonlinear effects in carbon nanotube-coated optical fibers

2011 Conference on Lasers and Electro-Optics Europe and 12th European Quantum Electronics Conference (CLEO EUROPE/EQEC), 2011

Research paper thumbnail of Electrical conductivity enhancement and toughening of Epoxy with SWCNT: A comparison between bulk resins and laminated composites

Research paper thumbnail of Continuous crack monitoring of metallic structures using carbon nanotube-based epoxy thin films

Research paper thumbnail of Binding energies for aluminum atom association complexes with dimethyl ether, diethyl ether and tetrahydrofuran

The Journal of Physical Chemistry, 1988

corresponds to an effective Hamaker constant of 4 X J, compared to approximately 6 X J for hydroc... more corresponds to an effective Hamaker constant of 4 X J, compared to approximately 6 X J for hydrocarbon across water and 2 X J for mica across water. That charge fluctuations of neutral surfaces are an unlikely candidate is supported experimentally by the numerous cases where no long-range attraction is observed between uncharged or weakly charged surfaces that are not h y d r o p h o b i~.~@~~ The above notwithstanding we have recently obtained some indications that an increased ionic strength decreases the range of the hydrophobic interaction measured between surfactant monolayer surfaces. This point, which is complicated by the fact that we also observe an increased charge density with increasing electrolyte concentration, will be addressed in a forthcoming publication. No hydrophobic attraction acts between surfaces composed of mixtures of hydrophobic and hydrophilic groups. Examples include surfaces of ethylene oxide groups3' and surfaces with adsorbed tetraalkylammonium ions.3z This indicates that a longrange hydrophobic attraction exists only between homogeneous hydrophobic areas larger than some critical size. For surfaces with 0, > 90° the range and magnitude of the attraction are rather insensitive to the exact value of the contact angle, provided the surfaces have been prepared under identical conditions. This suggests strongly that the hydrophobic interaction is related to the metastability of water films between hydrophobic surfaces."-13,33 The system is close to a liquid-vapor phase transition,

Research paper thumbnail of Four-wave mixing generation in carbon nanotube-coated optical fiber grating

IEEE Photonic Society 24th Annual Meeting, 2011

ABSTRACT Four-wave mixing (FWM) in single-walled carbon nanotubes (SWCNTs) wrapped on the claddin... more ABSTRACT Four-wave mixing (FWM) in single-walled carbon nanotubes (SWCNTs) wrapped on the cladding of a tilted fiber Bragg grating (TFBG) is demonstrated. FWM is generated by TFBG induced interaction of the core mode with the SWCNTs outer cladding. The wavelength tuning range of 8 nm is obtained.

Research paper thumbnail of Effect of the Localized Application of SWNT Modified Epoxy on the Interlaminar Shear Strength of Carbon Fiber Laminates

47th AIAA/ASME/ASCE/AHS/ASC Structures, Structural Dynamics, and Materials Conference<BR> 14th AIAA/ASME/AHS Adaptive Structures Conference<BR> 7th, 2006

This work investigates the interlaminar shear strength of unidirectional AS4/3501-6 laminates wit... more This work investigates the interlaminar shear strength of unidirectional AS4/3501-6 laminates with the interlaminar regions coated with a very thin film (≈20µm) of Functionalized Single Walled Nanotubes (F-SWNT) modified 3501-6 epoxy resin. These nanotubes were dispersed randomly in the epoxy before their application in the laminate. In addition, the rheological behavior of the 3501-6 epoxy and another brittle epoxy system was characterized using an oscillatory rheometer and the effect of SWNT on the resin viscosity is presented. The effect of the SWNTs on the cure and thermal degradation behavior of the epoxies are studied as well. I.

Research paper thumbnail of <title>High-resolution spectroscopy of small transition metal molecules: recent experimental and theoretical progress on group 5 diatomics</title>

Laser Techniques for State-Selected and State-to-State Chemistry II, 1994

ABSTRACT

Research paper thumbnail of Photoionization of Nb 3 CO and Nb 3 (CO) 2 :  Is CO Molecularly or Dissociatively Adsorbed on Niobium?

The Journal of Physical Chemistry A

The photoionization efficiency spectra of gas-phase Nb 3 CO and Nb 3 (CO) 2 have been acquired us... more The photoionization efficiency spectra of gas-phase Nb 3 CO and Nb 3 (CO) 2 have been acquired using a laserablation, photoionization mass spectrometer. The adiabatic ionization energies of the species are 5.82 (0.02 and 5.85 (0.02 eV, respectively, where error bars reflect precision, the values are accurate to within 0.1 eV. From these data and literature values of cation bond strengths, the bond energies of Nb 3-CO and Nb 3 CO-CO are found to lie within the 2.8-3.4 and 1.7-1.8 eV ranges, respectively. The former is most consistent with dissociatively adsorbed CO, while the latter may correspond to molecularly or dissociatively adsorbed CO. These conclusions are supported by density-functional theory calculations. In addition to properties of Nb 3 CO, the properties of the transition state to dissociative adsorption of CO have been calculated. It is found that the transition state lies lower in energy than the separated reagents. Spontaneous dissociation is expected to follow molecular adsorption of CO on Nb 3 , accordingly. Over the 1540-2220 cm-1 range, no infrared multiphoton dissociation of Nb 3 CO or Nb 3 (CO) 2 is observed, consistent with CO being dissociatively adsorbed for both species.

Research paper thumbnail of Interaction of Y, Y 2 , Mo, and Mo 2 with NH 3 . A Density Functional Study

The Journal of Physical Chemistry A, 2003

ABSTRACT

Research paper thumbnail of Reassessment of the first ionization potentials of copper, silver, and gold

Physical Review A, 1999

Brief Reports are accounts of completed research which do not warrant regular articles or the pri... more Brief Reports are accounts of completed research which do not warrant regular articles or the priority handling given to Rapid Communications; however, the same standards of scientific quality apply. (Addenda are included in Brief Reports.

Research paper thumbnail of Tailored SWCNT functionalization optimized for compatibility with epoxy matrices

Nanotechnology, 2012

We have modified single walled carbon nanotubes (SWCNTs) with well defined matrix-based architect... more We have modified single walled carbon nanotubes (SWCNTs) with well defined matrix-based architectures to improve interface interaction in SWCNT/epoxy composites. The hardener and two pre-synthesized oligomers containing epoxy and hardener moieties were covalently attached to the SWCNT walls by in situ diazonium or carboxylic coupling reactions. This way, SWCNTs bearing amine or epoxide terminated fragments of different molecular weights, which resemble the chemical structure of the cured resin, were synthesized. A combination of characterization techniques such as Raman and infrared absorption (FTIR) spectroscopy, elemental analysis and coupled thermogravimetry-FTIR spectroscopy were used to identify both functional groups and degree of functionalization of SWCNTs synthesized by the laser ablation and arc-discharge methods. Depending on the type of reaction employed for the chemical functionalization and the molecular weight of the attached fragment, it was possible to control the degree of functionalization and the electronic properties of the functionalized SWCNTs. Improved dispersion of SWCNTs in the epoxy matrix was achieved by direct integration without

Research paper thumbnail of Linear and Nonlinear Optical Properties of Carbazole-Containing Polymers

Molecular Crystals and Liquid Crystals Science and Technology. Section A. Molecular Crystals and Liquid Crystals, 1993

A systematic ab initio study of the optical as well as structural and electronic properties of th... more A systematic ab initio study of the optical as well as structural and electronic properties of the carbon nanotubes within density-functional theory in the local-density approximation has been performed. Highly accurate full-potential projected augmented wave method was used. Specifically, the optical dielectric function and second-order optical susceptibility (2) as well as the band structure of a number of the armchair ͓͑3,

Research paper thumbnail of Nanobeads Highly Loaded with Superparamagnetic Nanoparticles Prepared by Emulsification and Seeded-Emulsion Polymerization

Research paper thumbnail of High-resolution spectroscopy and photophysics of refractory molecules at low temperature: The C1Σ+-X1Σ+ system of ZrO

Journal of Molecular Spectroscopy, 1988

This paper shows that the technique of laser vaporization in conjunction with supersonic cooling ... more This paper shows that the technique of laser vaporization in conjunction with supersonic cooling and laser induced fluorescence is well suited for studies of the spectroscopy and photophysics of diatomic molecules of refractory character. In particular, the technique has been used to investigate the C'Z+-X'Z+ band system of ZrO. Rotational temperatures of ca. 25-35 K have been achieved. Fluorescence lifetimes of single rotational levels of C'Z+ (u = 0, 1) are reported together with those of the vibrational levels u = 0, 1, 2, and 3 of the B'II state. In light of these results, the photophysics ofthe C'Z+ state is discussed. In addition, the Franck-Condon factors and oscillator strengths for the vibronic transitions C'Z+-X'Z+ (0 + 0, 1, 2) and (1 + 0, 1, 2, 3) have been determined. A comparison with calculations is given. The O-O band of the C'Z'-X'Z' band system has been reinvestigated under higher resolution (-120 MHz). All five isotopic species (90ZrG, 9'ZrG, 92Zr0, 94Zr0, 96ZrG) have been clearly resolved, even for the R head, and data up to J = 29 are reported. Rotational constants and band origins for the X'Z+ (u = 0) and C'Z+ (u = 0) states of all five isotopic species have been evaluated. In the cases of 9oZrG, 94ZrG, and 96ZrG, comparisons with previous work are given and discussed. Advantages and disadvantages of the laser vaporization-supersonic cooling technique over conventional high-temperature methods for SpeCtrOSCOpiC studies are alS0 given. 0 1988 Academic PI=, IX.

Research paper thumbnail of Chemical Shift Imaging with Continuously Flowing Hyperpolarized Xenon for the Characterization of Materials

Journal of Magnetic Resonance, 2000

In this contribution we report new approaches to the MRI of materials using continuously produced... more In this contribution we report new approaches to the MRI of materials using continuously produced laser-polarized 129 Xe gas. This leads to vastly improved sensitivity and makes new kinds of information available. The hyperpolarized xenon is produced in a continuous flow system that conveniently delivers the xenon at low partial pressure to probes for NMR and MRI experiments. We illustrate applications to the study of micropore and other kinds of void space and show for the first time that with flowing hyperpolarized xenon it is possible to obtain chemical-shift-resolved images in a relatively short time.

Research paper thumbnail of Spectroscopy of the indium argon van der Waals complex: A high resolution study of the B 2Σ1/2←X2 2Π3/2 system

The Journal of Chemical Physics, 1993

The InAr van der Waals complex has been characterized by high resolution laser induced fluorescen... more The InAr van der Waals complex has been characterized by high resolution laser induced fluorescence excitation spectroscopy. Six vibronic bands of the B 2Σ1/2←X2 2&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;Pgr;3/2 transition have been observed and five of these (v’,0), where v’=1–5, have been rotationally analyzed. Rydberg–Klein–Rees potential curves were constructed for the B 2Σ1/2 state using the rotational and vibrational constants determined from these spectra.

Research paper thumbnail of Laser spectroscopy and density functional calculations on niobium monocarbide

The Journal of Chemical Physics, 1997

ABSTRACT A survey of the jet-cooled Nb12C and Nb13C radicals has been carried out between 13 500 ... more ABSTRACT A survey of the jet-cooled Nb12C and Nb13C radicals has been carried out between 13 500 and 18 000 cm−1 using laser-induced fluorescence and resonant two-photon ionization spectroscopy. Several vibronic bands belonging to at least six band systems have been identified. Three of these systems appear to belong to 2Π1/2–2Δ3/2 transitions in which the lower 2Δ3/2 state is the ground electronic state of the molecule. The other three systems also terminate to the same three 2Π1/2 upper states, but originate from a state lying 830 cm−1 above the X 2Δ3/2 state. This state is assigned as the A 2Σ+ state. The ionization potential has been determined to be 56 402±15 cm−1 or 6.9929±0.0018 eV using two-color photoionization efficiency spectroscopy. This value, combined with the ionization potential of Nb and the bond energy of NbC+, yields an improved bond energy of 5.39±0.15 eV for NbC. The (4,0) band of the B 2Π1/2–X 2Δ3/2 system has been studied at a resolution of approximately 0.005 cm−1 using laser-induced fluorescence spectroscopy. The nuclear magnetic hyperfine structure has been resolved in both states, and an analysis confirms that the 2Δ ground state arises from the σ2δ1 electron configuration in which the unpaired δ electron is a pure Nb 4d electron associated with the 4F term arising from the excited 5s24d3 electron configuration. Density functional calculations have been carried out on the lowest 2Δ, 2Σ+, 4Δ, 2Π, and 4(Π,Φ) states of the neutral and the 1Σ+, 3Δ, and 3(Π,Φ) states of the cations. These calculations fully support the experimental evidence for the ground state. © 1997 American Institute of Physics.

Research paper thumbnail of Ionization potentials and bond energies of TiO, ZrO, NbO and MoO

The Journal of Chemical Physics, 1998

[The Journal of Chemical Physics 109, 8980 (1998)]. Hans-Peter Loock, Benoit Simard, Sara Wallin,... more [The Journal of Chemical Physics 109, 8980 (1998)]. Hans-Peter Loock, Benoit Simard, Sara Wallin, Colan Linton. Abstract. ... Phys. 102, 4375 (1995). B. Simard, SA Mitchell, MR Humphries, and PA Hackett, J. Mol. Spectrosc. 129, 186 (1988). ...

Research paper thumbnail of Nonresonant two-photon mass analyzed threshold ionization and zero kinetic energy photoelectron investigation of the X̃ 2B1 ground state of CH2CO+ and CD2CO+

The Journal of Chemical Physics, 2002

Rotationally resolved nonresonant two-photon mass analyzed threshold ionization ͑MATI͒ and zero k... more Rotationally resolved nonresonant two-photon mass analyzed threshold ionization ͑MATI͒ and zero kinetic energy ͑ZEKE͒ photoelectron spectra of CH 2 CO ϩ and CD 2 CO ϩ are reported. The spectra are dominated by the origin band and totally symmetric a 1 vibrations, 4 ͑CϭC symmetric stretch͒ and 2 ͑CϭO asymmetric stretch͒ for CH 2 CO ϩ , and 1 ͑CϭO asymmetric stretch͒, 3 ͑CϭC symmetric stretch͒, and 4 (CD 2 scissor͒ for CD 2 CO ϩ. In addition, several weaker bands are observed in the MATI spectra: 3 (CH 2 scissor͒ in CH 2 CO ϩ ; b 1 vibrations 5 and 6 ͑CϭCϭO linear bend and CH 2 wag͒ in both isotopomers; b 2 vibration 8 (CD 2 rock͒ for CD 2 CO ϩ ; b 2 vibration 9 ͑CϭCϭO linear bend͒ for CH 2 CO ϩ ; as well as overtones and combination bands. Rotational structure of the origin band is dominated by three very strong ⌬K a ϭϮ1 bands with 2 orders of magnitude weaker ⌬K a ϭϩ3 bands. A similar ⌬K a ϭϮ1 three-band pattern is observed for the a 1 vibrational modes. For the b 1 modes a single-band pattern resulting from the ⌬K a ϭ0 selection rule is present. Fundamental wave numbers for six vibrational modes of CH 2 CO ϩ and seven modes of CD 2 CO ϩ are determined. Rotational analysis of the partially resolved ZEKE spectra yields the ionization potentials (77539.4Ϯ2.0 cm Ϫ1 for CH 2 CO and 77534.3Ϯ2.0 cm Ϫ1 for CD 2 CO) and rotational constants for the ground states of both ketene cations.

Research paper thumbnail of Rotational, fine, and hyperfine analyses of the (0,0) band of the D 3Π–X 3Δ system of vanadium mononitride

The Journal of Chemical Physics, 1993

ABSTRACT

Research paper thumbnail of Tilted fiber Bragg grating assisted nonlinear effects in carbon nanotube-coated optical fibers

2011 Conference on Lasers and Electro-Optics Europe and 12th European Quantum Electronics Conference (CLEO EUROPE/EQEC), 2011

Research paper thumbnail of Electrical conductivity enhancement and toughening of Epoxy with SWCNT: A comparison between bulk resins and laminated composites

Research paper thumbnail of Continuous crack monitoring of metallic structures using carbon nanotube-based epoxy thin films

Research paper thumbnail of Binding energies for aluminum atom association complexes with dimethyl ether, diethyl ether and tetrahydrofuran

The Journal of Physical Chemistry, 1988

corresponds to an effective Hamaker constant of 4 X J, compared to approximately 6 X J for hydroc... more corresponds to an effective Hamaker constant of 4 X J, compared to approximately 6 X J for hydrocarbon across water and 2 X J for mica across water. That charge fluctuations of neutral surfaces are an unlikely candidate is supported experimentally by the numerous cases where no long-range attraction is observed between uncharged or weakly charged surfaces that are not h y d r o p h o b i~.~@~~ The above notwithstanding we have recently obtained some indications that an increased ionic strength decreases the range of the hydrophobic interaction measured between surfactant monolayer surfaces. This point, which is complicated by the fact that we also observe an increased charge density with increasing electrolyte concentration, will be addressed in a forthcoming publication. No hydrophobic attraction acts between surfaces composed of mixtures of hydrophobic and hydrophilic groups. Examples include surfaces of ethylene oxide groups3' and surfaces with adsorbed tetraalkylammonium ions.3z This indicates that a longrange hydrophobic attraction exists only between homogeneous hydrophobic areas larger than some critical size. For surfaces with 0, > 90° the range and magnitude of the attraction are rather insensitive to the exact value of the contact angle, provided the surfaces have been prepared under identical conditions. This suggests strongly that the hydrophobic interaction is related to the metastability of water films between hydrophobic surfaces."-13,33 The system is close to a liquid-vapor phase transition,

Research paper thumbnail of Four-wave mixing generation in carbon nanotube-coated optical fiber grating

IEEE Photonic Society 24th Annual Meeting, 2011

ABSTRACT Four-wave mixing (FWM) in single-walled carbon nanotubes (SWCNTs) wrapped on the claddin... more ABSTRACT Four-wave mixing (FWM) in single-walled carbon nanotubes (SWCNTs) wrapped on the cladding of a tilted fiber Bragg grating (TFBG) is demonstrated. FWM is generated by TFBG induced interaction of the core mode with the SWCNTs outer cladding. The wavelength tuning range of 8 nm is obtained.

Research paper thumbnail of Effect of the Localized Application of SWNT Modified Epoxy on the Interlaminar Shear Strength of Carbon Fiber Laminates

47th AIAA/ASME/ASCE/AHS/ASC Structures, Structural Dynamics, and Materials Conference<BR> 14th AIAA/ASME/AHS Adaptive Structures Conference<BR> 7th, 2006

This work investigates the interlaminar shear strength of unidirectional AS4/3501-6 laminates wit... more This work investigates the interlaminar shear strength of unidirectional AS4/3501-6 laminates with the interlaminar regions coated with a very thin film (≈20µm) of Functionalized Single Walled Nanotubes (F-SWNT) modified 3501-6 epoxy resin. These nanotubes were dispersed randomly in the epoxy before their application in the laminate. In addition, the rheological behavior of the 3501-6 epoxy and another brittle epoxy system was characterized using an oscillatory rheometer and the effect of SWNT on the resin viscosity is presented. The effect of the SWNTs on the cure and thermal degradation behavior of the epoxies are studied as well. I.

Research paper thumbnail of <title>High-resolution spectroscopy of small transition metal molecules: recent experimental and theoretical progress on group 5 diatomics</title>

Laser Techniques for State-Selected and State-to-State Chemistry II, 1994

ABSTRACT

Research paper thumbnail of Photoionization of Nb 3 CO and Nb 3 (CO) 2 :  Is CO Molecularly or Dissociatively Adsorbed on Niobium?

The Journal of Physical Chemistry A

The photoionization efficiency spectra of gas-phase Nb 3 CO and Nb 3 (CO) 2 have been acquired us... more The photoionization efficiency spectra of gas-phase Nb 3 CO and Nb 3 (CO) 2 have been acquired using a laserablation, photoionization mass spectrometer. The adiabatic ionization energies of the species are 5.82 (0.02 and 5.85 (0.02 eV, respectively, where error bars reflect precision, the values are accurate to within 0.1 eV. From these data and literature values of cation bond strengths, the bond energies of Nb 3-CO and Nb 3 CO-CO are found to lie within the 2.8-3.4 and 1.7-1.8 eV ranges, respectively. The former is most consistent with dissociatively adsorbed CO, while the latter may correspond to molecularly or dissociatively adsorbed CO. These conclusions are supported by density-functional theory calculations. In addition to properties of Nb 3 CO, the properties of the transition state to dissociative adsorption of CO have been calculated. It is found that the transition state lies lower in energy than the separated reagents. Spontaneous dissociation is expected to follow molecular adsorption of CO on Nb 3 , accordingly. Over the 1540-2220 cm-1 range, no infrared multiphoton dissociation of Nb 3 CO or Nb 3 (CO) 2 is observed, consistent with CO being dissociatively adsorbed for both species.

Research paper thumbnail of Interaction of Y, Y 2 , Mo, and Mo 2 with NH 3 . A Density Functional Study

The Journal of Physical Chemistry A, 2003

ABSTRACT

Research paper thumbnail of Reassessment of the first ionization potentials of copper, silver, and gold

Physical Review A, 1999

Brief Reports are accounts of completed research which do not warrant regular articles or the pri... more Brief Reports are accounts of completed research which do not warrant regular articles or the priority handling given to Rapid Communications; however, the same standards of scientific quality apply. (Addenda are included in Brief Reports.

Research paper thumbnail of Tailored SWCNT functionalization optimized for compatibility with epoxy matrices

Nanotechnology, 2012

We have modified single walled carbon nanotubes (SWCNTs) with well defined matrix-based architect... more We have modified single walled carbon nanotubes (SWCNTs) with well defined matrix-based architectures to improve interface interaction in SWCNT/epoxy composites. The hardener and two pre-synthesized oligomers containing epoxy and hardener moieties were covalently attached to the SWCNT walls by in situ diazonium or carboxylic coupling reactions. This way, SWCNTs bearing amine or epoxide terminated fragments of different molecular weights, which resemble the chemical structure of the cured resin, were synthesized. A combination of characterization techniques such as Raman and infrared absorption (FTIR) spectroscopy, elemental analysis and coupled thermogravimetry-FTIR spectroscopy were used to identify both functional groups and degree of functionalization of SWCNTs synthesized by the laser ablation and arc-discharge methods. Depending on the type of reaction employed for the chemical functionalization and the molecular weight of the attached fragment, it was possible to control the degree of functionalization and the electronic properties of the functionalized SWCNTs. Improved dispersion of SWCNTs in the epoxy matrix was achieved by direct integration without

Research paper thumbnail of Linear and Nonlinear Optical Properties of Carbazole-Containing Polymers

Molecular Crystals and Liquid Crystals Science and Technology. Section A. Molecular Crystals and Liquid Crystals, 1993

A systematic ab initio study of the optical as well as structural and electronic properties of th... more A systematic ab initio study of the optical as well as structural and electronic properties of the carbon nanotubes within density-functional theory in the local-density approximation has been performed. Highly accurate full-potential projected augmented wave method was used. Specifically, the optical dielectric function and second-order optical susceptibility (2) as well as the band structure of a number of the armchair ͓͑3,

Research paper thumbnail of Nanobeads Highly Loaded with Superparamagnetic Nanoparticles Prepared by Emulsification and Seeded-Emulsion Polymerization

Research paper thumbnail of High-resolution spectroscopy and photophysics of refractory molecules at low temperature: The C1Σ+-X1Σ+ system of ZrO

Journal of Molecular Spectroscopy, 1988

This paper shows that the technique of laser vaporization in conjunction with supersonic cooling ... more This paper shows that the technique of laser vaporization in conjunction with supersonic cooling and laser induced fluorescence is well suited for studies of the spectroscopy and photophysics of diatomic molecules of refractory character. In particular, the technique has been used to investigate the C'Z+-X'Z+ band system of ZrO. Rotational temperatures of ca. 25-35 K have been achieved. Fluorescence lifetimes of single rotational levels of C'Z+ (u = 0, 1) are reported together with those of the vibrational levels u = 0, 1, 2, and 3 of the B'II state. In light of these results, the photophysics ofthe C'Z+ state is discussed. In addition, the Franck-Condon factors and oscillator strengths for the vibronic transitions C'Z+-X'Z+ (0 + 0, 1, 2) and (1 + 0, 1, 2, 3) have been determined. A comparison with calculations is given. The O-O band of the C'Z'-X'Z' band system has been reinvestigated under higher resolution (-120 MHz). All five isotopic species (90ZrG, 9'ZrG, 92Zr0, 94Zr0, 96ZrG) have been clearly resolved, even for the R head, and data up to J = 29 are reported. Rotational constants and band origins for the X'Z+ (u = 0) and C'Z+ (u = 0) states of all five isotopic species have been evaluated. In the cases of 9oZrG, 94ZrG, and 96ZrG, comparisons with previous work are given and discussed. Advantages and disadvantages of the laser vaporization-supersonic cooling technique over conventional high-temperature methods for SpeCtrOSCOpiC studies are alS0 given. 0 1988 Academic PI=, IX.

Research paper thumbnail of Chemical Shift Imaging with Continuously Flowing Hyperpolarized Xenon for the Characterization of Materials

Journal of Magnetic Resonance, 2000

In this contribution we report new approaches to the MRI of materials using continuously produced... more In this contribution we report new approaches to the MRI of materials using continuously produced laser-polarized 129 Xe gas. This leads to vastly improved sensitivity and makes new kinds of information available. The hyperpolarized xenon is produced in a continuous flow system that conveniently delivers the xenon at low partial pressure to probes for NMR and MRI experiments. We illustrate applications to the study of micropore and other kinds of void space and show for the first time that with flowing hyperpolarized xenon it is possible to obtain chemical-shift-resolved images in a relatively short time.

Research paper thumbnail of Spectroscopy of the indium argon van der Waals complex: A high resolution study of the B 2Σ1/2←X2 2Π3/2 system

The Journal of Chemical Physics, 1993

The InAr van der Waals complex has been characterized by high resolution laser induced fluorescen... more The InAr van der Waals complex has been characterized by high resolution laser induced fluorescence excitation spectroscopy. Six vibronic bands of the B 2Σ1/2←X2 2&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;Pgr;3/2 transition have been observed and five of these (v’,0), where v’=1–5, have been rotationally analyzed. Rydberg–Klein–Rees potential curves were constructed for the B 2Σ1/2 state using the rotational and vibrational constants determined from these spectra.

Research paper thumbnail of Laser spectroscopy and density functional calculations on niobium monocarbide

The Journal of Chemical Physics, 1997

ABSTRACT A survey of the jet-cooled Nb12C and Nb13C radicals has been carried out between 13 500 ... more ABSTRACT A survey of the jet-cooled Nb12C and Nb13C radicals has been carried out between 13 500 and 18 000 cm−1 using laser-induced fluorescence and resonant two-photon ionization spectroscopy. Several vibronic bands belonging to at least six band systems have been identified. Three of these systems appear to belong to 2Π1/2–2Δ3/2 transitions in which the lower 2Δ3/2 state is the ground electronic state of the molecule. The other three systems also terminate to the same three 2Π1/2 upper states, but originate from a state lying 830 cm−1 above the X 2Δ3/2 state. This state is assigned as the A 2Σ+ state. The ionization potential has been determined to be 56 402±15 cm−1 or 6.9929±0.0018 eV using two-color photoionization efficiency spectroscopy. This value, combined with the ionization potential of Nb and the bond energy of NbC+, yields an improved bond energy of 5.39±0.15 eV for NbC. The (4,0) band of the B 2Π1/2–X 2Δ3/2 system has been studied at a resolution of approximately 0.005 cm−1 using laser-induced fluorescence spectroscopy. The nuclear magnetic hyperfine structure has been resolved in both states, and an analysis confirms that the 2Δ ground state arises from the σ2δ1 electron configuration in which the unpaired δ electron is a pure Nb 4d electron associated with the 4F term arising from the excited 5s24d3 electron configuration. Density functional calculations have been carried out on the lowest 2Δ, 2Σ+, 4Δ, 2Π, and 4(Π,Φ) states of the neutral and the 1Σ+, 3Δ, and 3(Π,Φ) states of the cations. These calculations fully support the experimental evidence for the ground state. © 1997 American Institute of Physics.

Research paper thumbnail of Ionization potentials and bond energies of TiO, ZrO, NbO and MoO

The Journal of Chemical Physics, 1998

[The Journal of Chemical Physics 109, 8980 (1998)]. Hans-Peter Loock, Benoit Simard, Sara Wallin,... more [The Journal of Chemical Physics 109, 8980 (1998)]. Hans-Peter Loock, Benoit Simard, Sara Wallin, Colan Linton. Abstract. ... Phys. 102, 4375 (1995). B. Simard, SA Mitchell, MR Humphries, and PA Hackett, J. Mol. Spectrosc. 129, 186 (1988). ...

Research paper thumbnail of Nonresonant two-photon mass analyzed threshold ionization and zero kinetic energy photoelectron investigation of the X̃ 2B1 ground state of CH2CO+ and CD2CO+

The Journal of Chemical Physics, 2002

Rotationally resolved nonresonant two-photon mass analyzed threshold ionization ͑MATI͒ and zero k... more Rotationally resolved nonresonant two-photon mass analyzed threshold ionization ͑MATI͒ and zero kinetic energy ͑ZEKE͒ photoelectron spectra of CH 2 CO ϩ and CD 2 CO ϩ are reported. The spectra are dominated by the origin band and totally symmetric a 1 vibrations, 4 ͑CϭC symmetric stretch͒ and 2 ͑CϭO asymmetric stretch͒ for CH 2 CO ϩ , and 1 ͑CϭO asymmetric stretch͒, 3 ͑CϭC symmetric stretch͒, and 4 (CD 2 scissor͒ for CD 2 CO ϩ. In addition, several weaker bands are observed in the MATI spectra: 3 (CH 2 scissor͒ in CH 2 CO ϩ ; b 1 vibrations 5 and 6 ͑CϭCϭO linear bend and CH 2 wag͒ in both isotopomers; b 2 vibration 8 (CD 2 rock͒ for CD 2 CO ϩ ; b 2 vibration 9 ͑CϭCϭO linear bend͒ for CH 2 CO ϩ ; as well as overtones and combination bands. Rotational structure of the origin band is dominated by three very strong ⌬K a ϭϮ1 bands with 2 orders of magnitude weaker ⌬K a ϭϩ3 bands. A similar ⌬K a ϭϮ1 three-band pattern is observed for the a 1 vibrational modes. For the b 1 modes a single-band pattern resulting from the ⌬K a ϭ0 selection rule is present. Fundamental wave numbers for six vibrational modes of CH 2 CO ϩ and seven modes of CD 2 CO ϩ are determined. Rotational analysis of the partially resolved ZEKE spectra yields the ionization potentials (77539.4Ϯ2.0 cm Ϫ1 for CH 2 CO and 77534.3Ϯ2.0 cm Ϫ1 for CD 2 CO) and rotational constants for the ground states of both ketene cations.