Regional Climate and Air Quality

Research Project , Research Report 2001

Seiichiro KODA Dept. of Chemical System Engineering, the University of Tokyo
Jun HOROKAWA Res. Center for Advanced Science and Technology, the Univ. of Tokyo(Research Partners)
Mario MOLINA Massachusetts Institute of Technology, USA
Michael ROSSI Swiss Federal Institutes of Technology, Switzerland

Abstract

The photochemical behavior of absorbed species on ice surface was studied as one of the important heterogeneous chemical processes related to climate change and air quality. A multi-layer deposited ice film was prepared through water vapor deposition on a Ni plate in a vacuum chamber at 100 K, and was used as it was or after annealing at 140 K. NO2 was adsorbed as NO2 around 100 K on the ice film prepared as above, and irradiated by 193 nm excimer laser light. The time-of-flight (TOF) spectra of the main desorbed specipees, i.e. NO2, NO and O2 were measured by a quadrupole mass spectrometer. The relative yields of the products and their TOF sctra were dependent on the preparation condition of the ice film and also varied with the continuation of the laser irradiation. The TOF spectrum of NO from the non-annealed ice film consisted of distinctly different two components corresponding to the 1700 and 100 K translational temperature, respectively. NO was supposed to be a predissociation product from the electronically excited NO2 prepared through the photodissociation of N2O4. The behaviours of individual products were affected by the interaction of the primary photodissociation products with the ice film, in particular with the surface of inner micro-pores.

Keywords:

air quality, stratospheric clouds, ice film, surface photo-desorption, NOx