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Molecular Dynamics of Methylamine, Methanol, and Methyl Fluoride Cations in Intense 7 Micron Laser Fields

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journal contribution
posted on 30.10.2014, 00:00 by Bishnu Thapa, H. Bernhard Schlegel
Fragmentation and isomerization of methylamine (CH3NH2+), methanol (CH3OH+), and methyl fluoride (CH3F+) cations by short, intense laser pulses have been studied by ab initio classical trajectory calculations. Born–Oppenheimer molecular dynamics (BOMD) on the ground-state potential energy surface were calculated with the CAM-B3LYP/6-31G­(d,p) level of theory for the cations in a four-cycle laser pulse with a wavelengths of 7 μm and intensities of 0.88 × 1014 and 1.7 × 1014 W/cm2. The most abundant reaction path was CH2X+ + H (63–100%), with the second most favorable path being HCX+ + H2 (0–33%), followed by isomerization to CH2XH+ (0–8%). C–X cleavage after isomerization was observed only in methyl fluoride. Compared to random orientation, CH3X+ with the C–X aligned with the laser polarization gained energy nearly twice as much from laser fields. The percentage of CH3+ + X dissociation increased when the C–X bond was aligned with the laser field. Alignment also increased the branching ratio for H2 elimination in CH3NH2+ and CH3OH+ and for isomerization in CH3OH+.

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