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MO: Molekülphysik
MO 4: Posters Tuesday: Photoionisation
MO 4.7: Poster
Dienstag, 3. April 2001, 12:30–15:00, AT3
Dynamics of dissociative ionization of metal carbonyls by intense laser radiation — •Sergei Trushin, Werner Fuss, and Wolfram Schmid — Max-Planck-Institut fuer Quantenoptik, Postfach 1327, D-85741 Garching, Germany
We investigated ionization of the metal carbonyls Ni(CO)4, Fe(CO)5 and Cr(CO)6 in a linear time-of-flight mass spectrometer by 800 nm laser pulses of 110 fs FWHM in the intensity I range of (0.5-5)× 1013 W cm−2. Strong variation of degree of fragmentation (DF) and the ionic fragmentation pattern (FP) with I has been found. Ni(CO)4 shows a relatively large DF of around 1 already at the lowest I. It drops however with I. FP does not change in this intensity range. Such behavior is typical for resonance multiphoton ionization via short lived intermediate state. Fe(CO)5 shows opposite behavior: DF increases from 0.35 at low I to 770 at high I. DF in Cr(CO)6 slightly changes with I from 0.1 to 0.2, but FP changes significantly. At low I heavier fragments are dominant and at high I metal ion is the most abundant. Obviously resonances in the neutral species play a minor role in iron and chromium carbonyls as compared with Ni(CO)4. The difference between Fe(CO)5 and Cr(CO)6, especially the very strong fragmentation in the former case can be easily understood from the absorption spectrum of the ion. In Fe(CO)5+ the first excited state is only 1.3 eV above the ground state of the ion, while in Cr(CO)6+ it is at 5 eV.