Monochromator, programmed-scan

Multielemental Analysis Atomic emission spectroscopy is ideally suited for multi-elemental analysis because all analytes in a sample are excited simultaneously. A scanning monochromator can be programmed to move rapidly to an analyte s desired wavelength, pausing to record its emission intensity before moving to the next analyte s wavelength. Proceeding in this fashion, it is possible to analyze three or four analytes per minute. 

Programming instructions for scanning-stage stepper motors (or monochromator stepper motor, etc.) may contain a bit pattern that reflects the structure of the motor. For example, to step in one direction the POKE instructions to the motor address may be 3,6,12, and 9, which may look illogical until you consider the respective bit patterns, 0011,0110,1100, and 1001. Sending in reverse order will step the motor in the opposite direction. 

X-ray absorption spectroscopic measurements were carried out at the storage ring DORIS III (HASYLAB DESY, Hamburg, Germany) at the EXAFS II beam line, which was equipped with a Si (111) double-crystal monochromator. All spectra were recorded at room temperature in a step-scanning mode. For data analyses the program WinXAS [17] was used. 

Instructional programs relying on home-built scanning monochromator systems and low-power lasers have usually been limited to simple demonstrations of spectra of neat liquids. Carbon tetrachloride has been a perennial favorite because the spectrum is strong and easily interpreted [7,10]. A comparison of the spectra of carbon tetrachloride, chloroform, and methylene chloride is also common, as is a comparison of the spectra of benzene and cyclohexane. Even with these systems, polarization effects can be demonstrated and selection rules taught. Details of the vibrational spectra, particularly chlorine isotope effects, may be difficult unless the instrument resolution is 5 cm or better. Because FTIR instruments are generally available, comparison of the Raman and infrared spectra of liquids is often stressed. 

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