Experimental variables and matrix effects associated with the onset of ion generation in laser ionization of solid samples

Condensed‐phase laser ionization time‐of‐flight mass spectrometry of highly energetic nitro‐aromatic compounds

“…However, greater fragmentation, visible as ions at m/z <20, can also be seen. Figure 5 shows the threshold for the evolution of ions of specific m/z values with increasing energy per pulse for 12 The orthogonal extraction geometry used in our experiment allows a decoupling of the initial kinetic energy of the ions resulting from their escape velocities from the solid and the energy provided by the extracting field. Even under near threshold conditions, the kinetic energy and the energy spread of the ions are large once a Coulomb explosion occurs.…”

“…Differences of a few μJ may drastically change the information contained in the mass spectra. The laser energy per pulse can be easily controlled in our set‐up, thus allowing precise calculation of the minimum laser energy required to record a measurable signal and the evolution of the ion signal with laser energy. The onset of ion generation (ionization threshold) was determined by increasing the energy per pulse reaching the sample while monitoring the TOF mass spectra.…”

“…Details on the instrument can be found elsewhere . Figure shows the most relevant elements of the instrument.…”

“…Details on the instrument can be found elsewhere. [12] Figure 1 shows the most relevant elements of the instrument. Briefly, a pulsed Nd:YAG (5 ns, 266 nm) laser was used for ionization, with the laser energy being controlled in the interval between 0.2 and 7 mJ using a variable attenuator that allows continuous variation of the energy per pulse without modifications to the beam spatial profile.…”

Determination of plasma ignition threshold fluence during femtosecond single-shot laser ablation on metallic samples detected by optical emission spectroscopy

“…Some studies have mentioned in the past that reduction in laser uence may affect the stoichiometry of the ejected material (and that of plasma) due to the selective ablation (elemental fractionation) of elements with lower melting point. 16 Based on the previous experience with nanosecond excitation and mass spectrometry of binary and ternary alloys, 3 the ionization threshold of different elements in a given sample was different than that of the individual elements as pure samples. Thus, the threshold value in the samples was related to the average thermal properties of the individual constituents: the presence of elements of high melting point in the matrix turns the whole sample more refractory.…”