Yvette Houbrechts

New analysis of the A3Πi-X3Πi transition of BN

Abstract A new analysis of the A-X transition of BN, based on well-resolved spectra, has yielded B values which differ significantly from those of Douglas and Herzberg [Canad. J. Res. A. 18, 179–185 (1940)]. The new constants, B0′ = 1.449 cm−1 and B0″ = 1.548 cm−1 are in very good agreement with ab initio calculations of Karna and Grein (to be published).

The singlet bands of BN

The weak bands, tentatively attributed by Douglas and Herzberg (1940) to singlet bands of BN have been analysed and attributed to two distinct transitions of this radical: the c1 Sigma +-a1 Sigma + and the c1 Sigma +-b1 Pi transitions. Electron configurations of the new states are discussed.

The electronic spectrum of CCl

The A2 Delta -X2 Pi transition of CCl has been reinvestigated and the rotational analysis has been considerably extended. Precise molecular constants have been obtained for the two states involved. A new transition (B2 Sigma +- Sigma 2 Pi ) has been observed for the first time as well as diffuse absorptions in the vacuum ultraviolet.

Rydberg states of SiF in the vacuum ultraviolet

Ten Rydberg states of SiF have been observed below 2000 AA. Five of them have not been reported before. They all have been rotationally analysed.

The electronic states of silicon monofluoride: Rydberg states

Abstract SCF-CI calculations are reported for the Rydberg states converging to the ground state of the SiF + ion. The adjustment between the observed and calculated values for the energy of the first Rydberg B 2 Σ + state has allowed the characterization of 15 observed 2 Σ + and 2 Π Rydberg states. A value of 58960 cm −1 has been obtained for the ionization potential of SiF. The A 2 Σ + state appears to be a valence state with some Rydberg character.

Easy entry to the tricyclo(7,3,1,01-6)tridecane system

Abstract Michael addition of two equivalents of methyl vinyl ketone to dimedone, followed by acid-catalyzed cyclization give in 64% overall yield a strained tricyclic molecule with a spiro ring junction.

Rotational analysis of the C-X transition in SiCl

The C2 Pi -X2 Pi r transition in SiCl has been analysed rotationally. The C electronic state is a regular 2 Pi state. Improved molecular constants have been obtained for the C2 Pi state using the X2 Pi r molecular constants obtained in the B-X transition study.

Rotational analysis of the D-X transition in SiF

The D-X transition of SiF at 2100 AA has been analysed rotationally for the first time. The D state is shown to be a 2 Sigma -. Accurate molecular constants are given and electron configuration is discussed.

Cryo-optical testing of large aspheric reflectors operating in the sub mm range

The cryo-optical testing of the PLANCK primary reflector (elliptical off-axis CFRP reflector of 1550 mm x 1890 mm) is one of the major issue in the payload development program. It is requested to measure the changes of the Surface Figure Error (SFE) with respect to the best ellipsoid, between 293 K and 50 K, with a 1 μm RMS accuracy. To achieve this, Infra Red interferometry has been used and a dedicated thermo mechanical set-up has been constructed. This paper summarises the test activities, the test methods and results on the PLANCK Primary Reflector - Flight Model (PRFM) achieved in FOCAL 6.5 at Centre Spatial de Liege (CSL). Here, the Wave Front Error (WFE) will be considered, the SFE can be derived from the WFE measurement. After a brief introduction, the first part deals with the general test description. The thermo-elastic deformations will be addressed: the surface deformation in the medium frequency range (spatial wavelength down to 60 mm) and core-cell dimpling.

Dynamic holography for the space qualification of large reflectors

The next generation of infrared - sub mm space telescopes requires reflectors with large dimensions, high quality and, according to weight issues, are based on composite or new materials technology. The challenging tasks of on-ground testing are to achieve the required accuracy in the measurement of these reflectors shape and antenna structures and to verify their performance under simulated space conditions (vacuum, low-high temperatures). A holographic camera for the verification and validation of this type of reflector in a space environment is presented. A diffuser is implemented to measure the deformations of reflective surfaces in a more flexible way. The system has been made compatible with the vacuum conditions. Some elements of the holographic camera (camera lenses, CCD, crystal, optical fibre) have been adapted and tested under vacuum. The metrological certification of the whole system is realised by the measurement of a parabolic CFRP reflector with a 1.1 meter diameter. The results are compared to the one achieved with a high spatial resolution IR interferometer on the same reflector in laboratory conditions and under thermal vacuum conditions. This later test consists in measuring the deformations of the reflector between an initial state at a selected temperature and a final state at another temperature. The comparison between the high spatial resolution IR interferometer and this dynamic holographic method showed very good qualitative and quantitative agreement between the techniques, thus verifying the potential of this new Holographic approach.