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We will introduce the present knowledge of the turbulence profile and in particular we will emphasise the existence of a turbulence layer close to the ground. Then we will present the concept of Ground Layer Adaptive Optics and will provide estimates of performance expected from such systems and their potential for astronomical applications. Finally we will provide practical implementation concepts for two instruments at the VLT, MUSE and HAWK-I using multi-Laser Guide Stars and a large Deformable Secondary Mirror. The latter will also be described as its use is optimum for GLAO systems. To cite this article: N. Hubin et al., C. R. Physique 6 (2005).  相似文献
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More than 250 rotationally resolved vibrational bands of the A2B2-X2A1 electronic transition of 15NO2 have been observed in the 14 300-18 000 cm−1 range. The bands have been recorded in a recently constructed setup designed for high resolution spectroscopy of jet cooled molecules by combining time gated fluorescence spectroscopy and molecular beam techniques. The majority of the observed bands has been rotationally assigned and can be identified as transitions starting from the vibrational ground state or from vibrationally excited (hot band) states. An exceptionally strong band is located at 14 851 cm−1 and studied in more detail as a typical benchmark transition to monitor 15NO2 in atmospheric remote sensing experiments. Standard rotational fit routines provide band origins, rotational and spin rotation constants. A subset of 177 vibronic levels of 2B2 vibronic symmetry has been analyzed in the energy range between 14 300 and 17 250 cm−1, in terms of integrated density and using Next Neighbor Distribution. It is found that the overall statistical properties and polyad structure of 15NO2 are comparable to those of 14NO2 but that the internal structures of the polyads are completely different. This is a direct consequence of the X2A1-A2B2 vibronic mixing.  相似文献
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The 11 800-14 380 cm−1 frequency range has been scanned for rotationally resolved rovibronic transitions in the A2B2-X2A1 electronic band system of the symmetric (C2v) 16O14N16O and 18O14N18O isotopologues and in the corresponding electronic band system of the asymmetric (Cs) 18O14N16O isotopologue. The rotational analysis—reflecting minor differences in mass—in combination with symmetry induced spectral differences allows an identification of 68 16O14N16O vibronic levels, 26 18O14N18O vibronic levels and 51 18O14N16O vibronic levels. The bands are recorded using near infrared fluorescence spectroscopy and a piezo valve based pulsed molecular beam expansion of premixed 18O2 and 14N16O in Ar. The majority of the observed bands is rotationally assigned and can be identified as transitions starting from the vibrational ground state of one of the isotopologues. Numerous hot bands have also been identified. A comparison of the overall spectroscopic features of C2v vs. Cs symmetric species provides qualitative information on symmetry dependence of vibronic couplings.  相似文献
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Rotational spectra of quinoline and of isoquinoline have been observed in the centimeter- and millimeter-wave regions. The spectra were assigned on the basis of bands formed by high-J transitions, which were measured up to J″?128 and ν?234 GHz. Complementary measurements were also made on low-J, centimeter-wave spectra observed in supersonic expansion and with fully resolved nuclear quadrupole hyperfine structure. Accurate rotational, centrifugal distortion and hyperfine splitting constants for the ground states of both molecules are reported. The electric dipole moments for the two molecules were also determined from Stark effect measurements and are μa=0.14355(19), μb=2.0146(17), μtot=2.0197(17) D for quinoline, and μa=2.3602(21), μb=0.9051(14), μtot=2.5278(20) D for isoquinoline. The experimental observables were found to be rather accurately predicted by MP2/6-31G** ab initio calculations, and corresponding molecular geometries are also reported.  相似文献
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The spectrum of the nu(5) cis-bending vibration of ground state (X(2)Pi(u)) C(2)H(2)(+) has been recorded applying the method of laser induced reactions in a low-temperature 22-pole ion trap. It is obtained by counting the number of products of the reaction C(2)H(2)(+) (v(5) = 1) + H(2)--> C(2)H(3)(+) + H as a function of the laser wavelength. The vibronic transitions Delta-Pi and Sigma-Pi with their corresponding spin-orbit and Renner-Teller substructure have been observed. Using a perturbative analysis, the vibrational frequency has been determined to omega(5) = (710 +/- 4) cm(-1) and the Renner-Teller parameter epsilon(5) is on the order of 3 x 10(-2).  相似文献
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We propose a new method for recording the wave field. The method is based on that the angular spectrum of the field is modulated using an amplitude mask. It is shown that the new method ensures high spatial and angular resolutions. An optical scheme for implementing the method and an algorithm for reconstructing the wave-field phase from the measurement data are developed. Computer simulation of the experiment for recording the wave field on the basis of the proposed method is performed.  相似文献
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