NO(2) quantum yields from ultraviolet photodissociation of methyl and isopropyl nitrate.
NO(2) quantum yields from ultraviolet photodissociation of methyl and isopropyl nitrate.
复制标题
DOI：
10.1039/c001425g
复制
发表时间：
2010-06
期刊：
影响因子：
--
通讯作者：
P. G. Carbajo;A. Orr-Ewing
中科院分区：
文献类型：
--
作者：
P. G. Carbajo;A. Orr-Ewing
报道了甲基和硝酸异丙基(CH(3)ONO(2)和C(3)H（7)ONO(2)）光解后NO(2)形成通道（RO + NO(2)）在对流层相关波长308-320 nm下的量子产率Phi（NO(2)）。利用紫外（UV）激光吸收和腔衰荡光谱（CRDS）检测NO(2)光产物进行了测量。分析CRDS数据以获得NO(2)的量子产率，需要考虑到高斯强度激光束光解引起的NO(2)空间不均匀分布。在N(2)浴气存在、压力高达700 Torr、温度为294 K的条件下，甲基和硝酸异丙基在波长为308、315和320 nm时光解量子产率是一致的（不确定度<或=10% (2SD)）。在低于500托的浴气压力下观察到的NO(2)产率的明显下降，可能是由于内部激发的NO(2)的光化学形成，而在测量的时间尺度上，它没有被碰撞热化，或者是由于光产物的扩散。在308 nm和248 nm光激发波长处，本工作的量子产率值与先前报道的值一致。
Quantum yields, Phi(NO(2)), are reported for the NO(2) formation channel (RO + NO(2)) following photodissociation of methyl and isopropyl nitrate (CH(3)ONO(2) and C(3)H(7)ONO(2)) at the tropospherically relevant wavelengths of 308-320 nm. Measurements were made using ultra-violet (UV) laser absorption and cavity ring down spectroscopy (CRDS) detection of the NO(2) photoproducts. Analysis of CRDS data to obtain NO(2) quantum yields required account to be taken of the spatially inhomogeneous NO(2) distribution resulting from photolysis with a laser beam with a Gaussian intensity profile. Photodissociation quantum yields were measured to be unity (with <or=10% uncertainties (2SD)) for both methyl and isopropyl nitrate at wavelengths of 308, 315 and 320 nm in the presence of N(2) bath gas at pressures up to 700 Torr, and at a temperature of 294 K. An apparent decrease in the NO(2) yields, observed at bath gas pressures below 500 Torr, may result from photochemical formation of internally excited NO(2) which is not thermalized by collisions on the timescale of the measurement, or from diffusion of the photoproducts. Quantum yield values from the current work are in agreement with previously reported values at 308 and 248 nm photo-excitation wavelengths.