Diffuse background radiation

Cosmic chemical evolution and diffuse background radiation... 

As was mentioned in Section 12.1, there is a relationship between metal production and diffuse background radiation, perhaps more properly referred to as extragalac-tic background light (EBL), shown in Fig. 12.1, since most or all of it comes from individual galaxies. 

As the reflected radiation is emitted from the sample in a random direction, diffusely reflected radiation can be separated from, potentially sensor-blinding, specular reflections. Common techniques are off-angle positioning of the sensor with respect to the position(s) of the illumination source(s) and the use of polarisation filters. Application restrictions apply to optically clear samples with little to no scattering centres, thin samples on an absorbing background and dark samples. In either of these cases, the intensity of radiation diffusely reflected off such samples is frequently insufficient for spectral analysis. While dark objectives remain a problem, thin and/or transparent samples can be measured in transmission or in transflectance. 

Two parts of the flame may be distinguished an inner, luminescent cone (primary zone), and the outer, less luminescent surrounding area (secondary diffusion zone). The highest temperature is generally found directly above the inner cone. This region is therefore suitable for the measurement, thanks also to the fact that the background radiation is at its weakest here. 

There is also considerable variety in the astronomical goals. Seven experiments are devoted primarily to far Infrared surveys, seven to measurements of the cosmic background radiation, four to high resolution mapping and photometry, one to measurement of diffuse emission in the near Infrared, five to solar brightness, polarization, and spectra, and one to planetary spectra,... 

Leach S (2012) Why COBE and CN spectroscopy cosmic background radiation temperature measurements differ, and a remedy. Mon Not R Astron Soc 421 1325-1330 Indriolo N, McCall BJ (2012) Investigating the cosmic-ray ionization rate in the galactic diffuse interstellar medium through observation of Ha" ". Astrophys J 745 91-1-17... 

Polycyclic aromatic hydrocarbons (PAHs) Hydrocarbons in complex chains and agglomerated rings thought to be responsible for the diffuse emission Unes observed in dust nebulae in the near-infrared. These molecules form the lowest-mass end of the dust distribution and are responsible for ubiquitous diffuse emission in the 1- to 25-fxm galactic background radiation. 

See the discussion in section II.A.5.) COBE had three instruments for observing the background radiation the DMR, the EIRAS, and the diffuse infrared background experiment (DIRBE). 

---