Infrared multiple photon absorption and decomposition of 2-methyloxetane

Abstract

The decomposition of 2-methyloxetane by pulsed 10R34 radiation (984.4 cm^–1) from a TEA CO₂ laser has been studied in the fluence range 1.8–5.4 J cm^–2. The effective absorption coefficient is constant at pressures of 50m Torr and below but increases at higher pressures, an effect attributed to hole-filling by collisional rotational relaxation. At a fluence of 5.4 J cm^–2 the principal products are propene and ethene from the unimolecular processes (3) and (4).

[graphic omitted], The variation of the branching ratio with fluence shows that path (4) has a slightly higher threshold than path (3). Under conditions of ‘collisionless’ excitation addition of the inert gases xenon and cyclohexane reduces the extent of decomposition. Calculations based on RRKM rate constants and assumed intermolecular energy distributions show that a substantial fraction, but not all, of the irradiated 2-methyloxetane molecules, absorbs the 10R34 radiation. .