Short Wavelength Spectrometer

Infrared Space Observatory Short-Wavelength Spectrometer 300... 

Figure 4 The 2-20 xm spectrum of the protostar W33A obtained at a spectral resolution of 250 using the Short-Wavelength Spectrometer on board the Infrared Space Observatory. Except for the 10 xm silicate band, all features are due to simple molecules in ice mantles.

Figure 5 Absorption spectra of a number of protostars in the stretching region of CO and CO2 obtained by the Short-Wavelength Spectrometer on board the Infrared Space Observatory. The broad band at about 4.25 pm is due to the stretching mode of solid CO2. The narrow features in the 4.5-4.9 pm range are the rovibrational transitions of gaseous CO. The broader feature in the Q-band gap of this linear molecule is the stretching mode of solid CO. The narrow emission feature at about 4.66 pm in the spectrum of NGC 7538 IRS 1 is a hydrogen recombination line. These different sources are characterized by different temperatures of the absorbing gas and ices. The relative amounts of the rather-volatile molecule CO in the gas phase and the ice reflect this rather strikingly. Reproduced with permission of the Royal Society of Chemistry from van Dishoeck EF (1998) Faraday Discussions 109 31.

Figure 6 Absorption spectra of the bending mode of CO2 ice towards a number of protostars embedded in their natal molecular clouds obtained by the Short-Wavelength Spectrometer on board the Infrared Space Observatory at a spectral resolution of about 2000. The observed profiles show weak features at about 15.1 and 15.25 im as well as a shoulder at about 15.4 pm. The solid lines are laboratory spectra of the H20 CH30H C02 = 1 1 1 mixture deposited at 10 K and then warmed to temperatures in the range of 114 to 118 K. The sharp structure near 14.97 pm in some sources is due to the rovibrational transitions in the Q branch of gaseous CO2 which at this resolution pile up in one spectral resolution element. The individual P and R branch lines are too weak to be observable at this resolution.

Much higher spectral resolution ( 0.5 cm ) was obtained by the Infrared Space Observatory (ISO) in 1997 (see Coustenis etal., 1997 Coustenis Taylor, 1999). A disk-average spectrum of Titan by the Short-Wavelength Spectrometer (SWS) of... 

Tsuji, 2000 [342] detected water in emission in the spectrum of the M2 supergiant star /u, Cephei (M2 la) observed by the Short-Wavelength Spectrometer (SWL) on board ISO. The emission first appears in the 6 pm region and then in the 40 pm region (pure rotation lines) despite the rather strong dust emission. The intensity ratios of the emission features are far from those of the optically thin gaseous emission. From the observed emission features an optically thick water sphere of the inner radius about 2 R (corresponds to 1300 R ), T = 1500 K, and a colunm den-... 

One of the most direct methods is photoelectron spectroscopy (PES), an adaptation of the photoelectric effect (Section 1.2). A photoelectron spectrometer (see illustration below) contains a source of high-frequency, short-wavelength radiation. Ultraviolet radiation is used most often for molecules, but x-rays are used to explore orbitals buried deeply inside solids. Photons in both frequency ranges have so much energy that they can eject electrons from the molecular orbitals they occupy. 

The amine, amide and carboxy chromophores that are common to the general family of amino acids, peptides and proteins show absorption features in the short-wavelength part of the ultraviolet range to establish their associated CD features requires more sophisticated spectrometers. Much of the detailed conformational information gained from CD studies depends on data from this wavelength region. 

Association constants of up to lo M-1 in water were claimed for complexes between a nonapeptide and some pentapeptides (Sasaki, S. Takagi, M. Tanaka, Y Maeda, M. Tetrahedron Lett. 1996, 37, 85). The fitted UV curves described in this communication, measured at rather short wavelength, show an unusual behavior. In our hands attempted UV measurements of oligopeptide associations in water were hampered by nonlinear effects even with high-quality spectrometers of small stray light Similarly, NMR studies in our laboratoiy with amino acids such as phenylalanine as well as with peptides such as gly-phe-gly, gly-tyr-ala, and tetragylcine show no evidence for any association at concentrations up to 5 10 M. 

Since many important spectral lines from hot plasmas are emitted at very short wavelengths (< 300 A), the IPDA has been increasingly used in grazing incidence spectrometer systems on tokamak facilities. Hodge et al. (19) have placed an IPDA tangent... 

Wren s observation that many commonly used materials for optical components in vacuum u.v. spectrometers exhibit strong luminescence when irradiated at short wavelengths should be noted by workers in the field of v.u.v. fluorescence. 

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