Wavelength Conversion Factors

Exercise 27-10 The purpose of this exercise is to investigate the importance of the uncertainty principle for some kinds of spectroscopy other than nmr, as discussed in Section 27-1. (You may wish to use the wavelength-energy conversion factors given in Sections 9-3 and 9-4.)... 

Putting in the values of h and c, we find the conversion factor from wavelength to photon energy is... 

Combining this with the above formulae gives the following conversion factor, when the photon energy is in electron volts, and wavelength in nanometres ... 

It is generally very difficult to measure total gas column densities through a cloud, while it is relatively straightforward to measure die extinction (essentially optical depth) due to dust at some wavelength. The extinction is related to the total dust column density via a dust model, including a particle size distribution. These dust models are typically not unique, hence the additional constraint from the elemental abundances of dust constituents, in particular Si and Fe. Therefore, the conversion factor between the two is an important number, and significant efforts have been directed toward its measurement. 

The different types of outer shell electronic transitions that occur by absorption or emission of electromagnetic radiation in the UV, Visible and Near IR spectral regions are summarized in Figure 2.1. Since the electronic spectra can be plotted as a function of wavelength (nm), wavenumber (cm" ) or energy (eV), the conversion factors between the various units are reported in Table 2.1. 

Table 2.1 Conversion factors among wavelength % (nm), wavenumber V (cm ), energy E (eV).

Relative Irradiance for Different Wavelength Bands (nm) in % 300-400 400-800 300-800 Conversion Factor = Illuminance in lux/lrradiance (300-800 nm) in W/m2... 

DRS, the method of subtraction of the baseline requires special attention, especially because instructions in various commercial manuals might lead to erroneous results. The procedure adopted by the author involves (i) digital acquisition and storage of the reflectance spectrum of the white standard, Ro(v) over the range of wavenumbers v (cm1) of interest, where v = MX, X is the wavelength in cm and the conversion factor for the photon energy in... 

X rays of wavelength 0.154 nm strike an aluminum crystal the rays are reflected at an angle of 19.3°. Assuming that n = 1, calculate the spacing between the planes of aluminum atoms (in pm) that is responsible for this angle of reflection. The conversion factor is obtained from 1 nm = 1000 pm. 

The Duane-Hunt Law gives the conversion factor between energy and wavelength. Most X-ray systems express wavelength in angstroms and energy in keV. To convert between these units, Eq. (8.6) gives ... 

In this expression J is dimensionless, the half-life has units of seconds and the twentieth-power term in the numerator is a conversion factor with units of moles/photon. The integral overlap of the lamp emission and the chromophore electronic spectrum, EexZx, defines light absorption in photons mole-1 sec-1. EX is the average extinction coefficient for a given wavelength Interval with Zx equaling the lamp output over this same band. 

Spectroscopy detection of components through the measurement of their wavelengths in characteristic bands. The most frequently used instruments are infrared, ultraviolet, diffuse reflectance, etc. These properties are proportional to the concentrations of the components and may be related to their respective conversion factors. 

You are given the frequency of the light and asked to find its wavelength. Use Equation 7.1, which relates frequency to wavelength. You can convert the wavelength from meters to nanometers by using the conversion factor between the two (1 nm = 10 m). 

The factor 5.89 x IO-2 (or, more exactly, 5.8894 x IO-2) contains, besides the quantity 4n-2, all conversion factors, so that the normal vibrations can be inserted in the equations in wave numbers (cm ) instead of wavelengths, with the atomic masses in relative units. Force constants (/) are obtained from the equations in dyne/cm. They will have the order of magnitude 10 dyne/cm. It is, however, usual to change to mdyne/A by omitting the factor 10. ... 

One must be aware that X-ray wavelengths and conversion factors used in these references are somewhat different from those used here in the tables of X-ray emission and absorption energies, specified in the corresponding paragraphs (see Chapter 2.1.2.3, p. 223). Some critical comments on the Bearden-Burr compilation of core-level binding energies are to be found in [9], where values are presented for the M and N levels of Ru, Rh, and Pd. 

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