Ionisation and fragmentation dynamics of laser desorbed polycyclic aromatic hydrocarbons using femtosecond and nanosecond post-ionisation

• Published in: International journal of mass spectrometry Vol. 220; no. 1; pp. 69 - 85
• Main Authors: Robson, L., Tasker, A.D., Ledingham, K.W.D., McKenna, P., McCanny, T., Kosmidis, C., Tzallas, P., Jaroszynski, D.A., Jones, D.R.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 15.09.2002
• Subjects: Field ionisation; Laser desorption/femtosecond laser mass spectrometry; Multiply charged ions; Polycyclic aromatic hydrocarbons (PAHs); Multiply charged ions; Field ionisation; Laser desorption/femtosecond laser mass spectrometry; Polycyclic aromatic hydrocarbons (PAHs)
• ISSN: 1387-3806; 1873-2798
• DOI: 10.1016/S1387-3806(02)00823-0

Nanosecond laser desorption/femtosecond laser mass spectrometry (LD/FLMS) incorporating a reflectron time-of-flight mass spectrometer has been used to study the ionisation/fragmentation of polycyclic aromatic hydrocarbons (PAHs) in intense laser fields (7.0×10 14 to 9.3×10 15 W cm −2). Pulses of 80 fs, 800 nm have been used to post-ionise the PAHs anthracene, tetracene and pentacene. For each molecule strong singly and doubly charged parent ions are observed accompanied by fragmentation. In addition, strong triply charged parent ions (M 3+) are observed for anthracene and weaker M 3+ signals for tetracene and pentacene are also observed. Nanosecond post-ionisation (266 nm, 16 ns) spectra of the molecules have been recorded and are included for comparison with the femtosecond data. Similarities in the observed fragmentation pattern of low-mass fragments of the nanosecond and low intensity femtosecond spectra are highlighted. In addition, as the laser intensity increases, it is observed that fragmentation pathways preferentially switch from C m H 3 + ion yield to C m + production for m=2–5 at a critical intensity which is molecule dependent.