Electrostatic mode identification from a generalized wave-admittance vector

We show how cross-correlation of the fluctuations in LIF between two laser beams exciting optically isolated metastable lines can be used to identify and separate the power spectra of plasma electrostatic modes while using only a single measurement location.  A matrix of measurements of:
 
C(v,v',t')= <df(x,v,t)df(x,v',t-t')>t,
 
Fourier transformed over the time delay t', produces a Hermitian matrix when the two laser systems are tuned to the same set of Doppler-selected velocities.  We consider the effects of electrostatic waves on the LIF cross-correlation matrix.  Broad-band electrostatic waves are excited using a capacitive antenna driven with electrical white noise in a singly-ionized weakly-collisional ArII plasma column produced by a low power inductively coupled plasma source.
 
Modes can be identified by a generalized wave admittance which comes from the eigenvectors of the cross-correlation matrix.  We demonstrate the connection between this generalized impedance and the usual definition.  Other extensions of the technique will be considered.