No abstract

The translational, vibrational, and rotational characteristics of nitric oxide, NO, ejected by 351 nm photodissociation of tert-butyl nitrite, (CH3)3CONO, adsorbed on Ag(111) have been investigated using resonance-enhanced multiphoton ionization time-of-flight (REMPI-TOF) and interpreted using a direct excitation and collisional relaxation model. There are three translational energy components denoted as collisionless, intermediate, and thermalized. The collisionless component has characteristics matching those found for gas phase monomer photolysis. The thermalized component has characteristics expected for NO accommodated to the substrate temperature, while the more complex intermediate component is qualitatively describable in terms of collisions of nascent energetic NO with surrounding species as it exits into the gas phase. There are strong ν‘ ‘ = 1 and 2 but negligible ν‘ ‘ = 0 contributions to the collisionless component. The collisionless component is also characterized by high rotational excitation; Gaussian rotational distributions with J max = 24.5 ± 1 for ν‘ ‘ = 1 and 29.5 ± 1 for ν‘ ‘ = 2 provide reasonable fits. The translationally thermalized component is dominated by the ν‘ ‘ = 0 vibrational state and by a Boltzmann rotational distribution (T rot = 124 ± 30 K); i.e., all three modes of motion are thermalized. The vibrational and rotational characteristics of the intermediate translational component are more complex and will require simulation and angle-resolved REMPI for fuller elucidation.

The thermal properties of 2-naphthalenethiol, C10H7SH, dosed on Ag(111) at 150 K have been studied by temperature-programmed desorption (TPD) using time-of-flight mass spectrometry and Auger electron spectroscopy (AES). For low doses, no C10H7SH is observed in TPD, S-H bonds break below 235 K to form 2-naphthyl thiolate, C10H7S(a), and H(a), the latter desorbing as H2 below 300 K. For higher doses, dissociation is accompanied by C10H7SH desorption in a single unsaturable peak at 235 K. Reflecting the stability of the thiolate, there is negligible desorption between 300 and 500 K. Over a broad temperature range, 500-850 K, products desorb that couple C10H7 and C10H7S with H, with C10H7, or with C10H7S, but no H2 desorbs. Some products involve forming additional rings. At 850 K, the highest temperature probed, only H2S is desorbing. After TPD, AES detects a multilayer comprised of C and S with a C/S ratio of 3.1. A mechanism accounting for the products is presented. LA0113419