Propensity towards H photofragments in the photodissociation of CD₃NH₂ pre-excited to the first N–H stretch overtone

Abstract

Vibrationally mediated photodissociation combined with (2 + 1) resonantly enhanced multiphoton ionization detection of H and D photoproducts was used to assess selective bond fission in partially deuterated methylamine, CD₃NH₂. Jet-cooled action spectra and Doppler profiles of the H and D photofragments were obtained via ∼243.1 nm photodissociation of the parent containing two quanta of N–H stretch excitation. The multiband action spectra indicate that the energy flow out of the initially prepared N–H stretch to the bath states is on a picosecond time scale and that the 2v ₁₀ state (antisymmetric N–H stretch) is longer lived than the other states. Although the specificity attained by N–H stretch excitation was lost, the photofragment yield of H was nine times higher than that of D, indicating preferential N–H bond fission due to lower transition states on the excited state surface.

Keywords:

• Vibrationally mediated photodissociation
• Intramolecular vibrational redistribution
• Methylamine

Acknowledgements

The authors gratefully acknowledge support from the James Franck Binational German–Israeli Program in Laser–Matter Interaction and, in part, from the Israel Science Foundation founded by The Israel Academy of Science and Humanities.

Notes

†The Helen and Sanford Diller Family Chair in Chemical Physics.

Additional information

Notes on contributors

Salman Rosenwaks†

†The Helen and Sanford Diller Family Chair in Chemical Physics.