[en] Visible photoluminescence at room temperature has been observed in silicon particulates prepared in a silane rf plasma. Photoluminescence measurements were carried out on 'as-deposited' particulates and also on particulates suspended in the plasma during processing. The photoluminescence spectrum peaks at 730 nm and 780 nm (using the 488 nm line of an Ar+ ion laser), partly covering the visible region, for some of the particulates suspended in the plasma and for the others collected on a steel plate, respectively. It is suggested that the photoluminescence originates from nanocrystallites of silicon formed in these particulates. The in situ photoluminescence measurements in processing plasmas could serve as a diagnostic tool for plasmas involving particulate formation. (author) 4 figs., 20 refs