J. Cosléou

J. Cosléou
Université de Lille · Department of Physics

PhD

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66
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Publications

Publications (66)
Article
The narrow linewidth Vertical External Cavity Surface Emitting Laser (VECSEL) was used to record the high-resolution ammonia spectra in the 2.3 μm atmospheric transparency window at temperatures from 160 to 296 K. In the 4275-4356 cm−1 (∼ 2295-2339 nm) range 807 transitions were identified as belonging to the 14NH3, extending our previous room temp...
Article
The infrared gas-phase absorption spectrum of methane was used to determine its Clapeyron solid−gas equilibrium curve in the 40−77 K temperature range. For comparative purposes and to obtain more reliable results, two different optical experimental setups were used. At higher temperatures (53−77 K), a single pass cryogenically cooled cell was couple...
Article
The spectrum of (NH3)-N-15 has been investigated at room temperature in the 6367-6578 cm(-1) region using an external cavity tunable diode laser spectrometer. Particular care was taken to discriminate (NH3)-N-15 from the main species (NH3)-N-14 present as an impurity in the spectra. As a result, a new list of line positions and line strengths has b...
Article
Experiments on nuclear spin interconversion of ortho, para and meta nuclear spin isomers of the methane molecule have been undertaken in gas phase and cryomatrices. Only the latter environment have led to the observation of the nuclear spin conversion. In this study, a quantitative explanation is given for the first time by considering the coupling...
Article
Systematic analysis of the temperature dependence of the intensity ratio between already assigned and unassigned transitions enabled the determination of the most probable energy of the lower state of the unassigned transition. Such a procedure has been applied to transitions of 14NH3 ammonia in the range 6626–6805 cm−1 between 130 and 300 K. This...
Article
A spectroscopic study of ammonia molecule in the 2.3 μm water atmospheric window is presented. Compared to previous experimental works a narrow, broadly tunable, continuous laser source was applied in order to obtain high resolution spectra in this range. It was the first application of the newly developed Vertical External Cavity Surface Emitting...
Article
Analysis of the temperature dependence of the ratio of the intensity of two assigned and unassigned lines enables the determination of the most probable energy of the lower state of the unassigned transition. Such a new procedure has been applied to transitions of ammonia in the range 6626.0–6668.5 cm−1 between 122 K and 300 K. This represents a fi...
Article
Full-text available
CH 4 and other hydrogenated molecules of astrophysical interest like H 2 , H 2 O, H 2 CO, NH 3 , CH 3 OH, or C 2 H 4 play an important role for the chemistry in the interstellar medium (ISM) and in the protosolar nebula. Because of the spin ½ of the protons, these molecules exist in different nuclear spin configurations. In case of four protons as...
Article
The nuclear spin conversion (NSC) rate for a gas sample of NH is calculated in the framework of the quantum relaxation model. It is based on the knowledge of the vibration-inversion levels of the lowest vibrational states, the relaxation rates, and the intramolecular magnetic interactions. The magnitudes of the spin-spin and spin-rotation interacti...
Article
The rotational spectrum of NSF3 in the ground and v5 = 1 vibrational states has been investigated in the centimeter- and millimeter-wave ranges. R-branch (J + 1 <-- J) transitions for J = 0, 1 and Q-branch rotational transitions for the v5 = 1 vibrational state have been measured by waveguide Fourier transform microwave spectroscopy in the range 8-...
Article
The nuclear spin conversion of a molecule is the modification of the total nuclear spin I of its equivalent atoms. This phenomenon is observed by measuring the relaxation rate of a gas sample initially prepared with a population of spin isomers far from the equilibrium given by nuclear spin statistics. New experimental data obtained at low pressure...
Article
Full-text available
Context.Formaldehyde is an important diagnostic of the physical conditions in star forming regions. The temperature of formation is determined by measuring the relative abundance of para-H2CO and ortho-H2CO. The key hypothesis for this determination is that the ortho-para interconversion is strictly forbidden once the molecule is formed. However H2...
Article
The nuclear spin conversion rate depends on the collisions, which break the coherence created by magnetic intramolecular interactions between pairs of quasi degenerate levels belonging to the different spin isomers. The collisions act similarly to break the coherence created by a radiation field between two levels inducing pressure broadening of mo...
Article
The nuclear spin conversion is induced by hyperfine intramolecular magnetic spin–spin and spin–rotation interactions. The measurement of the conversion decay rates leads to the determination of these interactions strengths whose physical meaning is analysed in view of new ab initio calculations. It is also shown that the results derived from nuclea...
Article
The quadratic, cubic and semi-diagonal quartic force field of fluoroform has been calculated at the CCSD(T) level of theory employing a basis set of at least polarized valence triple zeta quality. This force field was used to predict the spectroscopic constants, including the parameters specific to the doubly degenerate vibrational states. The calc...
Article
When a gaseous sample of 13CH3 F is prepared with a spin-isomer population ratio (ortho and para forms) far from the equilibrium given by nuclear spin statistics, it relaxes towards this equilibrium with an exponential decay rate. This phenomenon, called nuclear spin conversion, is mainly governed by intramolecular spin-spin and spin-rotation inter...
Article
When a gas sample of 13CH3F is prepared with a population of spin isomers far from the equilibrium given by nuclear spin statistics, it relaxes towards this equilibrium with an exponential decay rate. This rate is increased by submitting the molecules to a static electric field, emphasizing the role of the magnetic intramolecular interactions and o...
Article
An analysis of the ν6=1 state of fluoroform is performed using rotational and high resolution infrared spectra. Previously radiofrequency data [Chem. Phys. Lett. 214 (1993) 265–270] and millimeter data [J. Mol. Spectrosc. 131 (1988) 1–8] were combined with new millimeter and infrared measurements, and a set of 27 parameters has been derived. A mult...
Article
Full-text available
When a gas sample of 13CH3F is prepared with a population of isomers (ortho and para forms) far from the equilibrium given by nuclear spin statistics, it relaxes towards this equilibrium with an exponential decay rate. This phenomenon called nuclear spin conversion is mainly governed by intramolecular spin-spin and spin-rotation interactions. In th...
Article
The υ6=2 vibrational state of the main isotopomer of trifluorosilane, 28SiHF3, has been investigated in the centimeter- and millimeter-wave ranges. Rotational spectra following the Δ J=1, Δk=Δ l=0 selection rule have been measured up to J=24 and K=23 and for both values of ∣l∣. Two types of direct l-type resonance transitions induced by the (Δ l=Δk...
Article
In the submillimeter range, from 345 to 410 GHz, 472 new rotational transitions in the vibrational ground state of hydrazine have been measured. The majority of recorded lines form eight K=2←1 Q-branches with J≤30, each branch being split due to internal rotation in hydrazine. New rotational transitions together with 443 known earlier have been fit...
Article
Four vibrational levels in the energy region around 1000 cm(-1) were studied. These were the v(5)=1 and v(8)=1 fundamental levels, both components of the v(9)=v(10)=1 combination level (l(9)=l(10)=+/-1 and l(9)=-l(10)=+/-1), and both components of the v(10)=3 overtone level (l(10)=+/-1 and +/-3). New FTIR spectra with a synchrotron radiation source...
Article
A global fit of microwave and millimeter-wave rotational transitions in the ground and first excited torsional states (v(t) = 0 and 1) of acetic acid (CH(3)COOH) is reported, which combines older measurements from the literature with new measurements from Kharkov, Lille, and NIST. The fit uses a model developed initially for acetaldehyde and methan...
Article
The nu(2) (nu(eff.) 854.841 cm(-1)) and 2nu(3) infrared bands (nu(eff.) 840.083 cm(-1)) of DSiF(3) have been studied with a resolution of 2.5 x 10(-3) cm(-1). Moreover, millimeter-wave transitions in the v(2) = 1 and v(3) = 2 states up to J" = 33 have been measured. The assignments and fit of the poorly resolved, compressed cluster-type 2nu(3) IR t...
Article
Full-text available
A new method is proposed for the experimental determination of the hyperfine coupling in molecules. The method is based on the level-crossing effect in the spin isomer conversion in alternating electric fields. An experiment performed with the 13CH3F molecules has revealed the strength of the off-diagonal in K () nuclear spin-spin coupling kHz, whi...
Article
First separation of the nuclear spin isomers of ethylene molecules (13C12CH4) and determination of the isomer conversion rate are reported. Experiment has revealed a linear increase of the conversion rate versus gas pressure equal to (5.2±0.8)·10−4 s−1/Torr. This indicates that the isomer conversion in 13C12CH4 is governed by quantum relaxation.
Article
The present paper deals with the analysis of the microwave, millimeter-wave, and infrared spectra of (28)SiHF(3) in its ground, v(6) = 1 and v(4) = 1 excited states. The former was observed up to 1055 GHz leading to the determination of one octic centrifugal distortion constant, L(J) = -0.0749(55) µHz. Furthermore the <k ||H ||k +/- 6> interaction...
Article
Full-text available
The nuclear spin conversion in CH3F molecules subjected to an alternating electric field was investigated experimentally. The conversion rate was found to be almost unaffected by low electric fields ( V/cm) but sharply increased tenfold when the electric field amplitude exceeds the values ( V/cm) sufficiently high to produce crossings of the ortho...
Article
The high-resolution FTIR spectra of deuterofluoroform (CDF3) at essentially Doppler-limited resolution of were studied in the regions of the ν2 (1111 cm−1) and ν3 (694 cm−1) fundamental and the ν2+ν3 (1802 cm−1) combination bands. The analysis of the two fundamental bands performed simultaneously with available submillimeter wave data leads to a si...
Article
The nu(5) fundamental band of trifluorosilane-d (SiDF(3)) at 627 cm(-1) was studied for the first time by high-resolution FTIR spectroscopy at a resolution of 2.4 x 10(-3) cm(-1). The analysis was performed simultaneously with available microwave and newly measured submillimeter-wave data in the approximation of an isolated degenerate fundamental l...
Article
Rotational spectra of PF3 in the degenerate vibrational state v4=1 have been measured in the radiofrequency, centimeter-, millimeter- and submillimeterwave range. 157 rotational transitions obeying the selection rules ΔJ=1, Δk=Δl=0 have been observed in the range 100–900GHz for 9≤J≤57 and 0≤k≤37. The J=1←0 transition and 246 direct l-type resonance...
Article
The rotational spectra of cyanoacetylene (HCCCN) were investigated between 148 and 474GHz. The assignments were obtained on the basis of a global analysis, which uses both vibrational and rotational data available for this molecule. The 876 new experimental frequencies concern 181 vibrational states (up to about 1750cm−1). The global analysis agree...
Article
This paper presents the analysis of the spectra of SiDF(3) in its vibrational ground and v(4) = 1 states. The pure rotational spectrum of the ground state was measured up to 903 GHz (J" = 65). Rotational, quartic, and sextic centrifugal distortion constants were accurately determined. Furthermore the parameter ||h(3) || = 7.64(11) x 10(-4) Hz was d...
Article
We have recorded a total of 12 FTIR spectra of monoisotopic OC(80)Se in different spectral regions with a resolution (1/maximum optical path difference) between 2.7 and 13.2 x 10(-3) cm(-1). These spectra spanned the range from 350 to 7800 cm(-1), many bands being studied with different p x L products in order to also detect weak hot bands. Altoget...
Article
This paper deals with the first study of high-resolution radio-frequency, centimeter-wave, millimeter-wave, and infrared spectra of the deuterated isotopomer of trifluorosilane, SiDF(3), in its lowest degenerate excited v(6) = 1 state. Following the work of E. I. Lobodenko, O. N. Sulakshina, V. I. Perevalov, and Vl. G. Tyuterev, (J. Mol. Spectrosc....
Article
The ground state rotational spectra of HDCO and D2CO have been measured from 5 to 2000 GHz. These new measurements together with older ones have been fitted to a standard A-reduced Watson-type Hamiltonian. The accuracy of the rotational and centrifugal distortion constants has been significantly improved. It has to be noted that it was necessary to...
Article
Acetic acid is of astrophysical interest, since several of its rotational transitions have been detected in interestellar space. It is also of theoretical interest as a relatively low barrier near-oblate internal rotor molecule with the methyl top axis approximately perpendicular to the near symmetric top axis. Preliminary experimental and fitting...
Article
The ground state rotational spectra of SiH3CN and its 29Si, 30Si, 13C, 15N, d1, d2, and d3 isotopic species have been measured by Fourier transform microwave spectroscopy and by millimeterwave spectroscopy. Accurate rotational, centrifugal distortion, and 14N and D nuclear quadrupole coupling constants have been derived. The dipole moment of the pa...
Article
The microwave spectra of acetic acid $(CH_{3}COOH)$ is complicated by a rather low internal rotation barrier of about $170 cm^{-1}$, leading to A-E splittings sometimes as big as a few gigahertz. In spite of its astrophysical interest (acetic acid was detected recently in the Sgr B2 interstellar $source^{a}$ using millimeter arrays), the millimeter...
Article
FTIR spectra of monoisotopic D3Si79Br covering the bands nu1 (a1, 1580.637 cm-1) and nu4 (e, 1615.085 cm-1) have been recorded with a resolution of 3 x 10(-3) cm-1. The rovibrational analysis revealed severe perturbations of the -5 </= KDeltaK </= 4 series of nu4 while nu1 and the high-K subbands of nu4 are almost unperturbed and served to determin...
Article
The degenerate fundamental vibrational levelv5= 1 has been studied using FTIR and sub-Doppler CO2laser-sideband spectroscopy, providing the most accurate vibration–rotation transition wavenumbers to this level measured so far, with resolvedA1–A2splittings of thekl= +1 andkl= −2 levels. Combined with rotational frequencies measured in thev5= 1 level...
Article
Millimeter-wave (mmw) spectra of D3Si79Br and D3Si81Br in the vibrational ground state have been recorded in the 150–650 GHz range. Furthermore, mmw spectra of D3Si79Br in thev3= 1 andv6= 1 states have been studied in some limited spectral ranges. FTIR spectra of monoisotopic D3Si79Br covering the bands ν3(a1, 418.650 cm−1), ν6(e, 464.254 cm−1), ν5...
Article
The theory of reduction of the effective rotational Hamiltonians of E.I. Lobodenkoet al.[J. Mol. Spectrosc.126,159–170 (1987)] is reviewed and completed to take into account correctly relations between the parameters of the reduced Hamiltonians for isolated vibrational states of speciesEofC3vmolecules. The effect of the phase factors on the symmetr...
Article
A least-squares fit is presented of 1105 far-infrared and 2860 microwave transitions in acetaldehyde, which sample rotational levels in all torsional states below the lowest-frequency small-amplitude vibration ν10. Four-fifths of these transitions, involving torsional states below the barrier (vt≤ 2), were treated in an earlier publication; here th...
Article
The rotational spectra of the ground vibrational state of the cis and trans isomers of crotononitrile have been measured in the frequency region 6-420 GHz. Accurate rotational constants, centrifugal distortion constants, and nuclear quadrupole coupling constants have been determined for both isomers. A barrier height of 1387.2(8) cal/mole for the i...
Article
High-resolution (0.003 cm−1) FTIR spectra of monoisotopic H3Si79Br have been studied in the ν3 and ν6 regions near 430 and 630 cm−1. We have fitted 2016 transitions for ν3, 631 for 2ν3−ν3, 1987 for (ν3 + ν6)−ν3, and 3251 for ν6, with standard deviations of the residuals of 0.206 × 10−3, 0.378 × 10−3, 0.370 × 10−3, and 0.113 × 10−3 cm−1, respectivel...
Article
We report here the results of a millimeter-wave study of all four possible bi-17O isotopic species of ozone, carried out in the frequency range from 49 to 393 GHz. Using Watson′s Hamiltonian expressed in the A-reduction form, the rotational constants and centrifugal distortion coefficients up to the sextic terms are accurately determined for each f...
Article
The infrared spectra of the $\nu_{2}$ and $\nu_{3}$ fondamental bands of $CDF_{3}$ have been recorded with a high resolution $(0.003 cm^{-1})$ FTIR spectrometer (BRUKER IFS 120HR). The K structure was analysed up to J = 50 for both states : 2488 lines of $\nu_{2}$ and 1956 lines of $\nu_{3}$ were assigned. We added also results from a previous anal...
Article
The rotational spectra of the ground vibrational state of the cis and trans isomers of crotononitrile have been measured in the frequency region of 6-420 GHz. Accurate rotational and centrifugal distorsion constants, and nuclear quadrupole coupling constants have been determined for both isomers. A barrier height of 1387.2(8) cal/mol for the intern...
Article
The ground-state rotational spectra of two isotopomers, (CH2)232S·HC14N and (CH2)232S·HC15N, of a complex formed by thiirane with hydrogen cyanide were analysed to give rotational constants, centrifugal distortion constants and 14N-nuclear quadrupole coupling constants. The spectroscopic constants were interpreted in terms of a geometry of the comp...
Article
The rotational spectrum of CH2--CHCN in its ground state and in its lowest-lying excited state was measured up to 1000 GHz. Different ways to check the assignment of the spectrum are discussed, and it is shown that the matrix of variance-decomposition proportions is very useful as a measure of the interdependence of the fitted parameters. These new...
Article
The millimetre- and submillimetre-wave spectra of the rotational transitions in the vibrational states υ2 = 1, υ3 = 2 and υ5 = 1 of 12CD3I were measured up to 393 GHz (J = 32). The vibrational states are perturbed especially by the x−y Coriolis resonance and “2,2” l-type interactions. Their parameters were determined by a simultaneous fit with the...
Article
Millimeter-wave and submillimeter-wave spectra of the rotational transitions in the v2 = 1 and v5 = 1 vibrational states of 13CH3F were measured up to 462 GHz. Far-infrared spectra of these transitions were measured in the region 30-65 cm-1 with a resolution of 0.0019 cm-1 using an interferometric spectrometer Bruker IFS 120 HR. Almost 700 lines in...
Article
The rotational spectrum of methyl cyanide-d3 was measured for the vibrational states v3 = 1, v4 = 1, v7 = 1, and v8 = 1, 3. The direct l-doubling transitions in the v8 = 1 state were also observed. The rotational parameters were determined for these states. A strong Coriolis resonance between the v4 = 1 and v7 = 1 states was observed and analyzed....
Article
The rotational spectrum of methyl cyanide in the vibrational state v4 = 1 has been measured up to 470 GHz (J
Article
The rotational spectrum of $CD_{3}CN$ has been measured up to 1500 GHz for the ground state and up to 400 GHz for several excited vibrational states: $v_{g}=1, 2,3, v_{4}=1, v_{7}=1, v_{3}=1$ and $v_{6}=1$. Many of these states are located between 700 and $1100 cm^{-1}$ and some of them are involved in the submillimeter emissions of $CD_{3}CN$. The...