Search results for "Linear molecular geometry"
showing 4 items of 24 documents
Observation of laser-induced field-free permanent planar alignment of molecules
2011
International audience; Permanent planar alignment of gas-phase linear molecules is achieved by a pair of delayed perpendicularly polarized short laser pulses. The experiment is performed in a supersonic jet, ensuring a relatively high number density of molecules with moderately low rotational temperature. The effect is optically probed on a femtosecond time scale by the use of a third short pulse, enabling a time-resolved birefringence detection performed successively in two perpendicular planes of the laboratory frame. The technique allows for an unambiguous estimation of the molecular planar delocalization produced within the polarization plane of the pulse pair after the turn-off of the…
Snapshot imaging of postpulse transient molecular alignment revivals
2008
Laser induced field-free alignment of linear molecules is investigated by using a single-shot spatial imaging technique. The measurements are achieved by femtosecond time-resolved optical polarigraphy (FTOP). Individual alignment revivals recorded at high resolution in ${\text{CO}}_{2}$, as well as simultaneous observation of several alignment revivals produced within the rotational period of the ${\text{O}}_{2}$ molecule are reported. The data are analyzed with a theoretical model describing the alignment experienced by each molecule standing within the interaction region observed by the detector. The temporal dynamics, intensity dependence, and degree of alignment are measured and compare…
Mean square radius of gyration and hydrodynamic radius of jointed star (dumbbell) and H-comb polymers
1996
Equations for the mean square radius of gyration and the hydrodynamic radius for jointed stars (dumbbells) and H-combs are derived, based on random flight statistics for each subchain. Comparision with literature data on computer simulations and experimental data for H-combs show good agreement for the g-value of the mean square radius of gyration even in good solvents. This suggests that for the mean square radius of gyration the relative dimension of a H-comb relative to the linear molecule of the same degree of polymerization is not altered significantly by long range interactions, as in the case of star polymers. For the hydrodynamic radius the situation is different. Fair agreement is …
High Resolution Coherent Raman Spectroscopy: Studies of Molecular Structures
1992
One of the main advantages of the non-linear coherent Raman techniques is the high resolution that can be achieved in rovibrational spectroscopy. Typically an instrumental function of the order of several thousandths of a wavenumber is routinely achieved in SRS or CARS experiments. Since the first recording of the stimulated Raman spectrum of 12CH4 in 1978 [1], numerous studies of molecules have been performed [2–8]. We have built a stimulated Raman experiment in Dijon in which particular attention has been paid to the frequency measurement of the Raman lines [9]. We will describe the application of our experiment to a wide variety of molecules over the last few years: linear molecules, sph…