Effect of negative ions on oscillating two stream instability of a laser driven plasma beat wave in a homogeneous plasma

A long wavelength plasma wave is driven by two co-propagating lasers with frequencies ωL1 and ωL2 such that ωL1 -ωL2 ≅ ωp. The plasma beat wave (ω0, k0) grows i amplitude and becomes susceptible to oscillating two stream instability, producing a low frequency electrostatic mode (ω, k) and two shorter wavelength Langmuir wave sidebands (ωs,f, ks,f) with ωs,f = ω±ω0 and ks,f = k±k0 in a plasma having positive ions, negative ions and electrons. It is shown that the growth rate, and the amplitudes and phases of the sidebands are influenced by the density n0n and temperature Tn of the negative ions. The effect of density on the instability is found to be more significant in a plasma that has positive and negative ions of higher temperatures