Secondary ion emission of phenylalanine as function of primary ion charge

Influence of the charge state of 1.16 MeV/u incident ions on the desorption process

“…A variation of several orders of magnitude in yield between nitrogen and uranium has been observed in experiments at G.S.I. Darmstadt [10].…”

“…Experimental studies of the influence of various entrance channel parameters on the desorption process have already been carried out using beams from heavy ion accelerators [7][8][9][10]. Measurements have been made over a large mass range (N to U), as well as some measurements at high energy (up to 5 Mev/u) for projectiles of intermediate mass.…”

“…This machine can accelerate a large range of ions (from 12C to 109 Ag or 134Xe) and its energy of Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphys:01987004802026100 1.16 Mev/u is close to the value where the desorption yield is maximum [5,9,11]. Experiments complementary to the previous measurements [10] have therefore been undertaken at Orsay, in collaboration with the Darmstadt group.…”

“…The thickness of the deposits was -2 000 A so as to obtain a homogeneous target. The ions emitted by bombardment with primary ions of several MeV/u are well known and exhibit characteristic peaks in the time-of-flight spectrum [9,10]. Positive or negative ions are detected when the acceleration grid is at a negative or positive potential respectively.…”

Delayed, gas‐phase ion formation in plasma desorption mass spectrometry

“…For H + ions and, to a lesser extent, hydrogen clusters H 2 + and H 3 + , formation from the uppermost surface layer of the target, very close ( < 30 Å) to the point of impact, has been established. 3 Coincidence experiments, 4 stoppingpower dependence studies, 5 and radial-velocity measurements combined with disappearance cross-section data 6 revealed that hydrocarbon fragments with small hydrogen content come from the hot regions within 40 Å from the MeV-ion track, while more saturated species originate further away from the track. The shortest time of ion formation via dissociation of the molecular bonds in the hottest regions was estimated to be ഠ 10 -14 s. 5 But ion formation is not only the acquisition of an electric charge by a neutral species.…”