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Jakarta Metropolitan Area (JMA) is an urban agglomeration in Indonesia where the air quality has dramatically changed from relatively clean to polluted. Economic growth, increased population, and village-to-city expansion marked the development of Jakarta and the satellite cities surrounding it, such as Bogor, Depok, Tangerang, and Bekasi. In line with human activities, large amounts of air pollutants are emitted and affect human health and vegetation. Ozone (O3) is a secondary air pollutant formed from volatile organic compounds (VOCs) and nitrogen oxides (NOx). This study aims to investigate the long-term trend of ozone precursors and ozone sensitivity in JMA from space. Trends analysis is studied using quantile regression. We used NO2 and formaldehyde (HCHO) column density from the Ozone Monitoring Instrument (OMI) aboard Aura Satellite from 2011 to 2022. Ozone sensitivity is derived from the ratio of HCHO and NO2 (FNR). The results show an upward trend in HCHO and a slight NO2 downward over JMA. In general, FNR changed from a predominantly VOC-limited regime in urban JMA to a transitional regime suggesting control of VOC and NOx is needed to reduce ozone concentration. Meanwhile, FNR in suburban and rural areas such as Bogor is toward a more NOx-limited regime.

The kinetics and absolute rate constants of the gas-phase reaction of the hydroxymethyl radical (C[H.sub.2]OH) with molecular oxygen were studied using laser photolysis/near-IR absorption spectroscopy. The results showed slight negative temperature dependence in the measured temperature region.

Thermal decomposition of disilane was investigated using time-of-flight(TOF) mass spectrometry coupled with vacuum ultraviolet single-photon ionization (VUV-SPI) at a temperature range of 675-740 K and total pressure of 20-40 Torr. Comparison between the experimental results and the kinetic simulation results suggested that about 70% of consumed disilane was converted to trisilane, which was observed as one of the main reaction products under the present experimental conditions.

The reactions of C1 atoms with XCH(sub 2)I (X=H, CH(sub 3), C1, Br, I) were studied using cavity ring-down spectroscopy in 25-125 Torr total pressure of N(sub 2) diluent at 250K. Absorption attributable to the formation of the XCH(sub 2)I-C1 adduct following the reaction of C1 atoms with XCH(sub 2)I (X=H, CH(sub 3), C1, Br, I) was measured as a function of temperature over the range 250-320 K.

The absolute absorption spectrum of the benzyl radical in the visible region measured by ring-down spectroscopy in the visible region measured by cavity ring-down spectroscopy is presented. The absorption cross sections reported would facilitate the quantification of the benzyl radical in future kinetic studies.

Cavity ring-down spectroscopy (CRDS) was used to calculate the electronic absorption spectrum of the allyl radical (CH2CHCH2) between 370 and 420 nm at 297 K. In conclusion, the absorption cross-section of the allyl radical at 402.9 nm was determined to be (2.0 plusmn 0.04) x 10(super -19) cm(super 2) molecule(super -1) through study of time-dependent absorption traces.

A deduction of the primary photodissociation mechanism of Si2H6 at 193 nm was made by photoproduct detection by laser-induced fluorescence (LIF) and time-resolved mass spectrometry techniques. Observation of the Si2H6 was conducted by the LIF method. No signal has been detected from SiH3, Si2H5, Si2H3 and Si2H4 in 193 nm photolysis. The importance of H2 elimination processes in Si2H6 produced in 193 nm photolysis was suggested by existing data combination.

A study of the reactions of Cl atoms with RI is conducted using cavity ring-down spectroscopy at a temperature of 233-313 K and at 100 Torr total pressure of N2 diluent. Visible absorption spectra of the RI-Cl adducts are recorded at 440-520 nm at 263 K.

Rate constants relevant to the thermal dissociation of Si(sub 2)H(sub 6) are calculated for the various multichannel unimolecular dissociations and chemical reactions. Quantum chemical calculations indicate that the energies of the saddlepoints for reactions R1 and R2 are lower than the energies of the product state.

Transient absorption spectra and decay profiles of hydroperoxy radical (HO2) are investigated using cw near-IR two-tone frequency modulation absorption spectroscopy at 297 K and 50 Torr in diluent of N2 in the presence of water. The results obtained suggest that the apparent rate of the HO2 self-reaction is enhanced by the formation of the HO2-H2O complex and its subsequent reaction.

The near-ultraviolet absorption spectrum of the phenoxyl radical (C6H5O(super .)) in 10-20 Torr of nitrogen diluent at 298 K is studied using cavity ring-down spectroscopy combined with pulsed laser photolysis. The absorption cross section of the phenoxyl radical was obtained by using a numerical fitting routine on the basis of a modeling of chemical reaction system.

Rate constants for the reactions of Si (3P, 1D, 1S) atoms with SiH4 are obtained using a combined laser photolysis/laser induced fluorescence technique. The results of the density functional theory calculations show that the reaction of Si(3P) atoms with SiH4 proceeds via a loose transition state.