B.3 Constants for unit conversion etc.
The following predefined constants are useful for conversion between units
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| Name | Value | Conversion from | Conversion to |
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| DEG2RAD | \(2 \pi / 360\) | Degrees | Radians |
| RAD2DEG | \(360 / (2 \pi )\) | Radians | Degrees |
| MIN2RAD | \(2 \pi / (360 \cdot 60)\) | Minutes of arc | Radians |
| RAD2MIN | \((360\cdot 60) / (2 \pi )\) | Radians | Minutes of arc |
| FWHM2RMS | \(1/\sqrt {8\log (2)}\) | Full width half maximum | Root mean square
(standard deviation) |
| RMS2FWHM | \(\sqrt {8\log (2)}\) | Root mean square
(standard deviation) | Full width half
maximum |
| PI | \(3.14159265...\) | \(\pi \) | |
| CELE | 1.602176487e-19 | Elementary charge (C) | |
| M_C | 299792458 | Speed of light in vacuum
(m/s) | |
| MELECTRON | 9.10938291e-31 | Electron mass (kg) | |
| ALPHA | 7.2973525698e-3 | Fine structure constant, \(\alpha \) | |
| RE | 2.8179402894e-5 | Thomson scattering
length (AA) | |
| E2K | 0.506773091264796 | Energy (keV) | Wavenumber (1/AA) |
| K2E | 1.97326972808327 | Wavenumber (1/AA) | Energy (keV) |
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