The pinhole-type glass nozzle originally introduced by Engelking for a corona excited supersonic expansion has been modified for a longer stability when heavy organic molecules are used for a precursor. The anode located just behind the nozzle opening on the high pressure side has been extended through the throat to avoid clogging the nozzle throat by decomposition products and soot deposits of heavy organic molecules in a corona discharge. The modified nozzle has been demonstrated for the vibronic emission spectrum of p-xylyl radical which shows much improved ratio of signal to noise due to the longer stability of corona discharge. (C) 2002 Published by Elsevier Science B.V.