P. Crozet

Claude Bernard University Lyon 1, Villeurbanne, Rhône-Alpes, France

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Publications (88)118.93 Total impact

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    ABSTRACT: Two-colour polarization labelling experiments have been used to explore the excitation spectrum of the rubidium dimer in the region 25 500-27 000 cm(-1), probing two mutually interacting states, identified from ab initio calculations as the 5(1)Σu (+) and 5(1)Πu states whose atomic dissociation products are Rb(5s) + Rb(5d). Treating the rather irregular progressions observed in the excitation spectra as transitions to single states with (numerous) local perturbations, we propose spectroscopic parameters and potential energy curves to describe the investigated levels. Observations cover more than 20 vibrational levels in the inner minima of both the 5(1)Πu and 5(1)Σu (+) states. Analysis was guided by ab initio calculations performed to describe the (1,3)Λg,u electronic states of Rb2 up to the Rb(5s) + Rb(5f) atomic asymptote. The theoretical potential energy curves are given in ASCII format in an electronic supplement to this paper.
    Full-text · Article · Aug 2015 · The Journal of Chemical Physics
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    ABSTRACT: We report an extensive series of transitions (including collisional transfer lines) from pure and mixed levels of the NaK A1Σ+ and bΠ3 states to the X1Σ+ state, observed at the Université Lyon 1 using Fourier-transform spectroscopy. We then combine these data with previously reported data on these states from emission from the B1Π and C1Σ+ states and from mutually perturbed levels of the D1Π and dΠ3 states. We obtain 2758 distinct term values: the full data set includes 11 624 term values, with many multiple determinations from transitions over a range of vibrational and rotational levels. The data are analyzed by fitting to potentials of the “Hannover” form [C. Samuelis et al., Phys. Rev. A 63, 012710 (2000)] plus spin-orbit (SO) functions in a simple Morse form, yielding an rms residual of approximately 0.029 cm−1. The empirical SO functions agree well with their ab initio counterparts obtained from electronic structure calculations based on nonempirical effective core potentials. From level energies of the A−b complex calculated from the fitted potentials and SO functions, we identify reasonable candidates for transitions between Feshbach resonance states and mixed singlet-triplet gateway levels of the A1Σ+−bΠ3 manifold, leading either to v=0 levels of the X state or to mixed singlet-triplet levels at higher energies that can be used for perturbation-facilitated double-resonance experiments.
    Full-text · Article · Jul 2015 · Physical Review A
  • Patrick Crozet · Georgi Dobrev · Cyril Richard · Amanda J. Ross
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    ABSTRACT: This paper provides a set of effective Landé factors gJ for the first rotational levels of vibrational levels 0 and 1 of the F 4Δ state of FeH, obtained from analysis of partially-resolved Zeeman patterns recorded in laser excitation, working at magnetic fields between 2000 and 5000 Gauss.
    No preview · Article · Sep 2014 · Journal of Molecular Spectroscopy
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    ABSTRACT: Laboratory spectra showing Zeeman patterns in some FeH lines susceptible to be used as magnetic probes in cool stellar atmostpheres have been recorded in the laboratory, and molecular Landé factors obtained from analysis. These Landé factors have been used to model some lines recorded in Stokes V polarisation in sunspot spectra at the solar telescope THEMIS.
    No preview · Article · Aug 2014 · Proceedings of the International Astronomical Union
  • A.N. Drozdova · X. Han · X. Dai · G. Wannous · P. Crozet · A.J. Ross
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    ABSTRACT: Double resonance experiments with one or two cw Ti:sapphire lasers have probed the 21Πg state of the rubidium dimer, whose potential minimum lies 22069.6 cm-1 above the minimum of the electronic ground state. Resolved fluorescence to the B1Πu state has been analyzed. Many of the rovibrational levels probed in this work lie below those observed in earlier work by Han et al. (2012). Combining new measurements with those available in the literature, observations now cover about 90% of the total well depth of the 2 1Πg state, whose dissociation products are Rb 4d(2D3/2) + Rb 5s (2S) atoms. We describe the 2 1Πg state with a set of Dunham-type polynomials and with an analytical potential curve determined from a direct fit of all available data, assuming Born-Oppenheimer mass dependence to fit 85Rb2 and 85Rb87Rb data simultaneously.
    No preview · Article · May 2014 · Journal of Molecular Spectroscopy
  • H. Harker · C. Richard · G. Tourasse · P. Crozet · A.J. Ross
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    ABSTRACT: We report molecular Landé factors for three Ω′ = 3/2 vibronic levels of NiH: E[17.8], D[17.6], and I[17.2], lying 17 000–18 000 cm−1 above the ground electronic state. The molecular Landé factors of these three states exhibit unusual variations with J and with parity. Also, molecular Landé factors of the D[17.6] excited electronic state are unexpectedly sensitive to Ni isotope substitution at low J. These observations provide evidence for extensive mixing among electronic states, deviation from Hund’s case (a) coupling, and the existence of a local perturbing state. We also report polarization-dependent discrepancies between experimental and theoretical spectral intensities [1] for transitions involving the I[17.2] excited electronic state.
    No preview · Article · Oct 2013 · Journal of Molecular Spectroscopy
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    ABSTRACT: Fourier transform records of A1Σu+−b3Πu→X1Σg+ and (2)1Πg→A1Σu+−b3Πu laser-induced fluorescence in hot rubidium vapor have identified more than 4500 rovibronic term values in the spin-orbit-coupled A1Σu+ and b3Πu states of Rb2. We report a 4×4 coupled-channel deperturbation analysis of some 6100 term energies in 85Rb2 and 85Rb 87Rb, including term values taken from papers by Salami et al. [Phys.Rev.A 80 022515 (2009)], Amiot et al. [ Phys.Rev.Lett. 83 2316 (1999)], and Amiot [J.Chem.Phys. 93 8591 (1990)]. Spin-orbit and spin-rotation interactions between A1Σu+ and b3Πu(Ω=0,1,2) are taken into account explicitly, fitting to analytical potential curves of the interacting A1Σu+ and b3Π0u states and to r-dependent diagonal and off-diagonal spin-orbit-coupling functions. The resulting mass-invariant fitting parameters reproduce 96% of all available experimental term values of the A−b complex for all Rb2 isotopes (covering 93% of the A1Σu+ potential energy well) with a standard deviation of 0.005 cm−1, matching experimental uncertainties estimated to be ≤0.01 cm−1.
    No preview · Article · Aug 2013 · Physical Review A
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    ABSTRACT: Fourier transform spectra of collisionally induced fluorescence following isotopically selective laser excitation of NiH at ∼550 nm have located an excited Ω = 1/2 state of NiH lying 17900 cm above the electronic ground state. This is identified as v = 0 of a Π1/2 state originating from an Ni 3d4sF configuration. Emission from this Ω′ = 1/2 state occurs predominantly to v″ = 0 and 1 of the Σ and W2 Π1/2 ligand field states, locating elusive f parity levels of W2 Π1/2 up to 5600 cm above the first rotational level of the electronic ground state, X1 Δ5/2. Collisionally induced fluorescence following laser excitation at lower energies has also been recorded in the presence of a magnetic field (0.7–1 T), at Doppler limited resolution. Effective Landé factors gJ for rotational levels of the v = 0 and 1 levels of the low-lying Ω″ = 5/2 and 3/2 components of the Δ and Π states of NiH have been derived from partially resolved Zeeman patterns. About 1600 transitions recorded in field-free conditions have been reduced to term energies relative to the lowest level of the ground state. They confirm strong spin-orbit mixing between the low-lying ligand-field states.
    No preview · Article · Sep 2012 · Molecular Physics
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    ABSTRACT: We have used a hollow cathode sputtering source, flowing a mixture of 10 % H_2 in Ar ˜45 standard cm^3/minute to form FeH radicals. Sputtering from iron required currents ≥ 250 mA. A permanent magnet was placed 2--3 cm below the cathode, generating magnetic fields 3000--4500 Gauss. Output from a Sirah Matisse Ti:sapphire laser was focused to a beamwaist < 1mm to probe a reasonably homogeneous region of the magnetic field, with the laser operating around 1 μm for the 0-0 band and 890 nm for the 1-0 band of the F ^4Δ←X ^4Δ system in FeH. The magnetic field is calibrated to 0.5 % accuracy from the Zeeman response of the Ar I line at 10958.339 cm-1. Several spectra have been taken for lines of the R branches of the F ^4Δ7/2←X ^4Δ7/2 and F ^4Δ5/2←X ^4Δ5/2 sub-bands, showing resolved structures at Doppler resolutions. Unresolved structures are seen for the Q and P transitions. Landé factors have been determined for the upper state (relying on ground state data from LMR work. We gratefully acknowledge financial support from the French agency ANR, and from the CNRS (PNPS programme) for this work.}) either from fits to peak positions, or by simulating observed profiles when this was impossible. The Landé factors have been used to deduce a magnetic field of 2200 Gauss in sunspots from lines near 1 μm observed at the solar telescope THEMIS (Tenerife) in July 2011. Stokes V profiles were recorded at the telescope, for optimum sensitivity. The magnetic field deduced from atomic lines (Ti,Fe) is around 10 % higher than that found from FeH, compatible with molecules forming at higher altitudes in the solar atmosphere. J.M. Brown, H. Korsgen, S.P. Beaton, & K.M. Evenson, J. Chem. Phys. 124 234309 (2006)
    No preview · Article · Jun 2012
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    ABSTRACT: We report laboratory measurements of the Zeeman response of lines in the 0-0 Wing-Ford band of the F-X system (λ ~ 1 μm) of FeH, measured in magnetic fields 0.3 - 0.5 Tesla. New Landé factors are used to deduce the magnetic field in sunspots from Stokes V profiles recorded at the solar telescope THEMIS. The magnetic field deduced from atomic lines (Ti, Fe) is slightly higher than that found from FeH.
    No preview · Article · Feb 2012 · EAS Publications Series
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    C. Richard · P. Crozet · A. J. Ross · D. W. Tokaryk
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    ABSTRACT: Fourier transform spectra of collisionally induced fluorescence following isotopically selective laser excitation of NiH at ˜ 550 nm has allowed us to locate an exited Omega' = 1/2 state of NiH lying 17900 Cm-1 above the electronic ground state. We identify this as v = 0 of a ^2Pi1/2 state, originating from the Ni^+ 3d^84s^1 ^2F configuration, from the ab initio studies published by Zou and Liu in 2007. Emission from the [17.9]0.5 state occurs to v''= 0 and 1 of the ^2Sigma^+ and ^2 Pi1/2 low-lying ligand field states, locating hitherto elusive ^2 Pi1/2 f parity levels to within 0.01 Cm-1. Collisionally induced fluorescence following laser excitation at lower energies has been recorded in the presence of a magnetic field (0.7 - 1 Tesla), at Doppler resolution. The partially resolved Zeeman patterns have been used to derive effective Landé factors g_J for the v=0 and 1 levels of the low-lying Omega'' = 5/2 and 3/2 states ({^2Delta} and ^2Pi states from Ni^+ 3d^9). These are compared with predictions from a revised fit of zero-field energy levels, now including the new observations concerning the Omega'' = 1/2 states. W.L. Zou, W.J. Liu. J. Comp. Chem. 28 (2007) 2286-98
    Preview · Article · Jun 2011
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    ABSTRACT: We present a Doppler-limited transmission spectrum of the rubidium dimer, suitable for frequency calibration of near infrared (e.g. Ti:sapphire) excitation experiments in the region 9500–12 300 cm−1. It provides an abundant source of reference peaks that can be used in a graphic environment to calibrate short (<1 cm−1) scans of excitation spectrum. This is a sequel to an iodine atlas in ascii format [1] that we routinely use for the same purpose in the visible spectrum. The rubidium spectrum was recorded at an instrumental resolution of 0.018 cm−1. Absolute precision is expected to be ∼0.005 cm−1, and relative precision ∼0.003 cm−1. The Rb2 A–X transmission spectrum is available in ascii format, as supplementary material.Graphical abstractResearch highlights► Reference spectrum 815–1050 nm. ► Rb2 molecular atlas. ► Calibration of laser excitation spectra near 1 micron.
    No preview · Article · Nov 2010 · Journal of Molecular Spectroscopy
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    ABSTRACT: We have found that dispersed laser induced fluorescence spectra of NiH produced in a discharge source are characterized by remarkably strong emission bands from upper state levels populated by collisional energy transfer. When the molecules are formed in the presence of a static magnetic field, magnetic response can be measured simultaneously for many transitions, under identical experimental conditions. Working with magnetic fields of 5000 - 10000 Gauss, the Zeeman patterns of many lines are at least partially resolved, at Doppler limited resolution. If the initial excitation process is chosen to be isotopically selective, the entire spectrum features emission from a single isotopologue, which simplifies analysis considerably. {M_J} selectivity is also possible in some cases. Measurements have been made so far for 58NiH and 60NiH. The magnetic response of NiH in the low-lying states W_1 2Pi 3/2, X_2 2Delta3/2, and X_1 2Delta5/2 states evidently c hanges with v''. This illustrates the effects of mixing between states, described by the supermultiplet 3d^9 complex model given by Gray et al. The intensity distributions of the M_J components in these spectra will be discussed. R. Vallon et al. Astrophys. J. 696 172 (2009) J. A. Gray, M. Li, T. Nelis, and R. W. Field, J. Chem. Phys., 95 7164 (1991)
    No preview · Article · Jun 2010
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    ABSTRACT: Recent laboratory measurements of isotopologue 58NiH by laser excitation around 17000-18000 cm-1 in a magnetic field have allowed us to study several electronic systems of this molecule. Zeeman patterns were analysed using literature values for ground state Landé factors. Effective electronic Landé factors geff have been determined. They show strong variation with parity in the rotational levels in some Omega'=3/2 states, giving evidence for extensive mixing between excited electronic states. McCarthy et al. JCP 107 (1997) 4179
    No preview · Article · Jun 2010
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    ABSTRACT: Extensions of the recently introduced ``Morse/long-range'' (MLR) potential function form allow a straightforward treatment of a molecular state for which the inverse-power long-range potential changes character with internuclear separation. Use of this function in a direct-potential-fit analysis of a combination of new fluorescence data for 7,7Li2, 6,6Li2, and 6,7Li2 with previously reported data for the A(1Σu+) and X(1Σg+) states yields accurate, fully analytic potentials for both states, together with the analytic ``adiabatic'' Born-Oppenheimer breakdown radial correction functions which are responsible for the difference between the interaction potentials and well depths for the different isotopologues. This analysis yields accurate well depths of De=8516.709(+/-0.004) and 8516.774(+/-0.004) cm-1 and scattering lengths of 18.11(+/-0.05) and 23.84(+/-0.05) A˚ for the ground-states of 7,7Li2 and 6,6Li2, respectively, as well as improved atomic radiative lifetimes of τ(2p)=27.1018(+/-0.0014) ns for 7Li(2p) and 27.1024(+/-0.0014) ns for 6Li(2p).
    Full-text · Article · Oct 2009 · Chemical Physics
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    ABSTRACT: We present experimentally derived potential curves and spin-orbit interaction functions for the strongly perturbed A 1Σu+ and b 3Πu states of the rubidium dimer. The results are based on laser-induced fluorescence and optical-optical double-resonance polarization spectroscopy measurements combined with earlier laser-induced fluorescence data. We used an analytic potential (Hannover form) incorporated in a discrete variable representation of the Hamiltonian matrix for numerical energy-level calculation. A previous vibrational assignment of the A levels is confirmed, and very probable vibrational assignment for the b levels is also obtained. Currently, the rms residual of our fit is 0.053 cm−1 as compared to the typical experimental uncertainties that are estimated to be 0.005 cm−1. Fitted diagonal and off-diagonal spin-orbit functions are obtained and compared with ab initio calculations by all electrons and effective core pseudopotential methods. Analysis of the computational results yields an explanation for the ubiquitous single minima in these spin-orbit functions, which can be represented approximately by Morse-type functions.
    Full-text · Article · Aug 2009 · Physical Review A
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    ABSTRACT: We present experimentally derived potential curves and spin-orbit interaction functions for the strongly perturbed ASigma1u+ and bPi3u states of the rubidium dimer. The results are based on laser-induced fluorescence and optical-optical double-resonance polarization spectroscopy measurements combined with earlier laser-induced fluorescence data. We used an analytic potential (Hannover form) incorporated in a discrete variable representation of the Hamiltonian matrix for numerical energy-level calculation. A previous vibrational assignment of the A levels is confirmed, and very probable vibrational assignment for the b levels is also obtained. Currently, the rms residual of our fit is 0.053cm-1 as compared to the typical experimental uncertainties that are estimated to be 0.005cm-1 . Fitted diagonal and off-diagonal spin-orbit functions are obtained and compared with ab initio calculations by all electrons and effective core pseudopotential methods. Analysis of the computational results yields an explanation for the ubiquitous single minima in these spin-orbit functions, which can be represented approximately by Morse-type functions.
    Full-text · Article · Aug 2009 · Physical Review A
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    ABSTRACT: A metal sputtering source suitable for laboratory production of metal hydrides is described. Sputtering from pure nickel or iron in an Ar/H(2) discharge is analyzed at low resolution. High resolution laser excitation and dispersed fluorescence spectra of NiH have also been recorded. The source has been designed to operate with a ferromagnetic circuit for Zeeman spectroscopy. Signals from the source are strong enough to record dispersed fluorescence from NiH by Fourier transform interferometry in magnetic fields up to 1 T. We establish that FeH can also be formed in this source.
    No preview · Article · Aug 2009 · The Journal of Physical Chemistry A
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    ABSTRACT: Laser-induced fluorescence from the lowest vibrational levels of the A 1Sigma_u+ state of Rb2 have been recorded on an FT spectrometer. Global depertubation gives vibrational numbering in the A 1Sigma_u+ and perturbing b 3Pi_u states.
    No preview · Conference Paper · Apr 2009
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    ABSTRACT: Red and orange bands of laser-induced fluorescence in NiH have been recorded on a Fourier transform interferometer at Doppler resolution. The spectra show strong transitions to low-lying vibronic states which are not thermally populated in a laboratory source, and therefore do not appear in laser excitation spectra, but which would be expected to contribute significantly to any stellar spectrum. The strongest bands belong to the G[Ω' 5/2]-X 2 2Δ3/2, I[Ω' 3/2]-X 2, and 2Δ3/2I[Ω' 3/2]-W 12Π3/2 systems. Measurements are reported for 58NiH, 60NiH, and 62NiH.
    Full-text · Article · Apr 2009 · The Astrophysical Journal

Publication Stats

989 Citations
118.93 Total Impact Points

Institutions

  • 1986-2015
    • Claude Bernard University Lyon 1
      • Laboratoire de spectrométrie ionique et moléculaire (LASIM)
      Villeurbanne, Rhône-Alpes, France
  • 1996-2014
    • French National Centre for Scientific Research
      Lutetia Parisorum, Île-de-France, France
  • 1991-2014
    • University of Lyon
      Lyons, Rhône-Alpes, France
  • 1995
    • University of Oxford
      Oxford, England, United Kingdom
  • 1993-1994
    • University of New Brunswick
      • Department of Physics
      Fredericton, New Brunswick, Canada