Photodissociation of ammonia at 193.3 nm: Rovibrational state distribution of the NH2(Ã 2A1) fragment

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Abstract
The rovibrational state distribution of the nascent NH2(Ã 2A1) fragments generated by 193.3 nm photodissociation of a room temperature sample of NH3 is determined through an analysis of a major portion (6000–13 000 cm−1) of the NH2(Ã 2A1→X̃ 2B1) near infrared emission spectrum obtained by time‐resolved Fourier transform infrared emission spectroscopy. The NH2(Ã) fragments are observed to be formed predominantly in their zero‐point vibrational level, with substantial rotational excitation about their a‐inertial axis up to the limit of the available energy, ∼3150 cm−1, but with little excitation about the other axes. The pattern of this energy disposal is discussed within the framework of existing knowledge regarding the form of the NH3 Ã state potential energy surface on which the dissociation occurs. The essential features are entirely consistent with a direct carry over, into the fragment, of the out‐of‐plane bending vibrational motion introduced in the parent molecule by the photoexcitation process.