Isotopic relations for tetrahedral and octahedral molecules

International audienceThe study and analysis of heavy spherical-top molecules is often not straightforward. The presence of hot bands and of many isotopologues can lead to a high line congestion very difficult for assignment. In this work, using a low-order model we have derived very simple isotopic relations in order to determine initial parameters of the analysis. We also show that an identical approach can be used for XY 4 and XY 6 molecules and all these results are illustrated by the comparison of numerical computations and experiments

Analytical expression of tensorial rotational operators for semi-classical interpretation of molecular spectra. Relations between molecular Hamiltonian parameters in different formalisms

International audienceWe present a formal development of the tensorial rotational Hamiltonian using symbolic calculations. Algebraic manipulations thanks to the open-source Maxima software allow us to get formal expressions of use for various molecular spectroscopy problems. We first present some simple applications to the so-called semi-classical approach that allows the study of level structures in the molecular rotational energy spectrum. Then, we perform some comparisons between the tensorial approach and Watson’s Hamiltonian, giving exact effective molecular parameter correspondence formula between the two formalisms

The bending triad of the quasi-spherical top molecule SO2F2 in the 550 cm-1 region

International audienceThe analysis of the v(3)/v(7)/v(9) bending triad of SO2F2 has been recently performed with the Watson's Hamiltonian up to octic terms employing 79 rovibrational parameters but including only the first order Coriolis interaction terms, fixed to ab initio values [H. Burger, J. Demaison, F. Hegelund, L. Margules, I. Merke, J. Mol. Struct. 612 (2002) 133-141]. Since SO2F2 is a quasi-spherical top, it can also be considered as derived from the SO42- sulfate ion. We have thus developed a new tensorial formalism in the O(3) > Td > C2v group chain [M. Rotger, V. Boudon, M. Loete, J. Mol. Spectrosc. 216 (2002) 297-307]. This approach allows a systematic development of rovibrational interactions and makes global analyses easier to perform even for complex polyad systems. We present here an application of this model to the analysis of the bending triad, with the same set of microwave assignments and almost the same set of infrared assignments as in the previous study of Burger et al. It appears that we need to expand our Hamiltonian to a lower degree than the "classical" one (six instead of eight) when including also the second order Coriolis interactions. Our fit does not include more parameters. Furthermore, all of them are determined and the standard deviation of the rotational transitions is twice smaller. The analysis has been performed thanks to the C-2 upsilon TDS program suite, which is freely available at the URL: http://icb.u-bourgogne.fr/OMR/SMA/SHTDS/C2VTDS.html

IR SPECTROSCOPY WITH A DOUBLE MODULATION SIDEBAND TECHNIQUE

Author Institution: Abteilung Physikalische Chemie, Universit\""{a}t Ulm, Einsteinallee; Laboratoire de Spectronomie, Mol\'{e}culaire et InstrumentationWe have applied both microwave and radio frequency modulation to $CO_{2}$ laser lines using only one CdTe modulator. As a result, a grid of closely spaced ($\Delta\nu\times 1 MHz$) and tunable infrared frequencies is generated. This technique was used to perform infrared-infrared double resonance experiments on the molecules $^{28}SiH_{4}$ and $^{28}SiF_{4}$ and to observe the Stark splitting due to extremely small dipole moments. As a preliminary result we obtained values for several dipole moment parameters which agree with measurements performed with other techniques

The high overtone and combination levels of SF6 revisited at Doppler-limited resolution: A global effective rovibrational model for highly excited vibrational states

International audienceSulfur hexafluoride is an important prototypal molecule for modeling highly excited vibrational energy flow and multi quanta absorption processes in hexafluoride molecules of technological importance. It is also a strong greenhouse gas of anthropogenic origin. This heavy species, however, features many hot bands at room temperature (at which only 30 % of the molecules lie in the ground vibrational state), especially those originating from the lowest, v 6 =1 vibrational state. Using a cryogenic long path cell with variable optical path length and temperatures regulated between 120 and 163K , coupled to Synchrotron Radiation and a high resolution interferometer, Doppler-limited spectra of the 2ν 1 + ν 3 , ν 1 + ν 2 + ν 3 , ν 1 + ν 3 , ν 2 + ν 3 , 3ν 3 , ν 2 + 3ν 3 and ν 1 + 3ν 3 from 2000 to 4000 cm-1 near-infrared region has been recorded. Low temperature was used to limit the presence of hot bands. The spectrum has been analyzed thanks to the XTDS software package. Combining with previously observed weak difference bands in the far infrared region involving the v 1 , v 2 , v 3 =1 states, we are thus able to use the tensorial model to build a global fit of spectroscopic parameters for v 1 =1,2, v 2 =1, v 3 =1,2,3. The model constitutes a consistent set of molecular parameters and enable spectral rovibrational simulation for all multi-quanta transitions involving v 1 , v 2 and v 3 up to v 1−3 =3. Tests simulation on rovibrational transitions not yet rovibrationally assigned are presented and compared to new experimental data

Feasability of the detection of vibration induced faults in connectors by reflectometry

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Feasability of the detection of vibration induced faults in connectors by reflectometry

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