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V A = V S + V o (+): Star and earth are receding V B = V S – V o (-): Star and earth are approaching. Doppler-shift formula:. 1 Å = 1 x 10 -10 m c = 2.9989 x 10 8 m/s. Doppler Effect and Line Broadening. Thermal broadening Rotational broadening Collisional broadening
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VA = VS + Vo (+): Star and earth are receding VB = VS – Vo (-): Star and earth are approaching
Doppler-shift formula: 1 Å = 1 x 10-10 m c = 2.9989 x 108 m/s
Doppler Effect and Line Broadening • Thermal broadening • Rotational broadening • Collisional broadening • Zeeman effect (magnetic broadening) Line broadening can be due to a variety of causes
Rotational Broadening Rotation will also cause broadening of spectral lines through the Doppler effect
Comparison Values • Orbital velocity of earth: • 2.98 x 104 m/s • Earth-sun distance: • 1.496 x 1011 m