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qspec.doppler  (  f v alpha return_frame = 'atom'  )[source]

The Doppler-shifted frequency $f^\prime = \begin{cases}f\gamma(v)(1 - \frac{v}{c}\cos(\alpha)), & \mathrm{atom}\\ f[\gamma(v)(1 - \frac{v}{c}\cos(\alpha))]^{-1}, & \mathrm{lab}\end{cases}$

Parameters:
farray_like

The frequency $f$ of light (arb. units).

varray_like

The velocity $v$ of a body (m/s).

alphaarray_like

The angle $\alpha$ between the velocity- and the light-vector in the laboratory frame (rad).

return_framestr

The coordinate system for which the frequency is returned. Can be either 'atom' or 'lab'.

Returns:
outndarray

the Doppler-shifted frequency $f^\prime$ in either the rest frame of the atom or the laboratory frame ([f]).

Raises:
ValueError

return_frame must be either 'atom' or 'lab'.

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