A flood gun 10 for charge neutralization of an analysis region R.sub.a of a sample S downstream of the flood gun, comprising: a first source 30 of electrons; a second source 50 of positively charged particles; and an extraction and focusing assembly 60,64, arranged to: (i) extract a first, electron beam from the first source and focus the first beam to a first flood area A.sub.e at the analysis region; and (ii) extract a second, positive particle beam from the second source and focus the second beam to a second flood area A.sub.i at the analysis region. The electron beam and the positive particle beam may both be extracted and focused simultaneously, in a single mode of operation or, alternately, in a dual mode of operation. A corresponding method of providing charge neutralization and a spectroscopic system for secondary particle emission analysis are disclosed.