Synchrotron and Free Electron Laser Sources of Infrared Radiation

Abstract

In this article, we describe the infrared sources that are based on electron accelerators. Such sources have novel properties that allow them access to unique applications, which are complementary to those with laboratory‐based sources. Specifically, accelerator‐based sources are extremely bright, and are pulsed. Synchrotrons are broadband sources that are up to 1000 times brighter than black body sources and with pulses that are of order 100 ps long. Free electron laser sources are 6–10 orders of magnitude brighter than synchrotron radiation sources, but are narrow band. The pulse lengths are sub‐picosecond. Both sources have pulse repetition frequencies of around 100 MHz. This article explains concepts of brightness and how these sources fit into the menu of available sources for vibrational spectroscopy.

Instrumentation for Far‐Infrared Spectroscopy

“…The spectral energy density of a blackbody at 1400 K is almost 5800 times weaker at 10 cm 1 , and about 60 times weaker at 100 cm 1 , than it is at 1000 cm 1 . Since the sensitivity of any measurement of a MIR or FIR spectrum is directly proportional to the spectral energy density of the source, it is apparent that FIR sources should be as hot as possible and have an emittance of close to unity.…”

“…Although Nernst glowers can be operated at higher temperature than Globars, they become quite transparent below about 200 cm 1 , so that their emissivity drops to the point that they are of little use as FIR sources, despite their high temperature. Below 100 cm 1 , the emissivity of a Globar  also becomes low and it is customary to use a high-pressure mercury lamp for measurements between ¾50 cm 1 and the onset of the microwave region of the spectrum. The reason why mercury lamps have proved to be so successful for FIR spectrometry is because emission from the plasma reinforces the emission from the hot quartz envelope of the lamp.…”

Stability analysis of primary emulsion using a new emulsifying agent gum odina

“…Changes in peaks in wave numbers between 2700 cm -1 and 720 cm -1 may be possibly due to interaction between ketonic and aldehyde groups in the fatty acids by formation of H-bonding or weak bondings such as Van der Waal forces or dipole moments, since the zone between 2690 cm -1 and 2840 cm -1 are the medium intensity and 1720 cm -1 -1740 cm -1 and 1710 cm -1 -1720 cm -1 are strong intensity carbomile stretching vibration zone and 720 cm -1 -725 cm -1 is the weak intensity bending vibration zone of CH 2 rocking [30]. Reaction at the 1646 cm -1 and 718 cm -1 might be due to the opening of α and β unstauration and interaction with OH-group or H due to heating or CH 2 rocking.…”

“…Peak variations at 2665 cm -1 and 3457 cm -1 of samples exposed to oxygen were probably due to the possible weak bond formation between OH and COOH of water and fatty acid respectively, since these are the known stretching vibration zones of OH and C=O [30]. Peak variations at 1437 cm -1 and 1148 cm -1 could be due to α-CH 2 bending or C-C-C bending of fatty acid carbons, since, 1400 cm -1 -1450 cm -1 are the bending vibration zone of α-CH 2 and 1148 cm -1 is the medium intensity C-C bending vibration zone [30].…”

“…Peak variations at 1437 cm -1 and 1148 cm -1 could be due to α-CH 2 bending or C-C-C bending of fatty acid carbons, since, 1400 cm -1 -1450 cm -1 are the bending vibration zone of α-CH 2 and 1148 cm -1 is the medium intensity C-C bending vibration zone [30]. Thus, upon FTIR spectrum analysis, it may be stated that the emulsion is not susceptible to oxidation, since the reactions were due to physical bond formations.…”