Unattenuated solar photo rate coefficients and excess energies for dissociation, ionization, and dissociative ionization are presented for atomic and molecular species that have been identified or are suspected to exist in the atmospheres of planets, satellites (moons), comets, or as pollutants in the Earth atmosphere. The branching ratios and cross sections with resonances have been tabulated to the greatest detail possible and the rate coefficients and excess energies have been calculated from them on a grid of small wavelength bins for the quiet and the active Sun at 1 AU heliocentric distance.

Solar photo rates for planetary atmospheres and atmospheric pollutants

The vibrational and K-type rotational levels of the [Xtilde] 2 B 1 and A 2 A 1 states of NH2 and H2O+ have been fitted by least squares to give sets of Born-Oppenheimer potential curves for the combining electronic states. The model used allows a simultaneous fit to all the observed vibronic levels for each of the two molecules, using a large amplitude formalism and making no approximations other than to neglect Fermi (anharmonic) resonance effects. An accurate description of the effects of orbital angular momentum on the level positions in the two molecules has been obtained, and relative transition moments have been calculated for the vibronic bands of the A 2 A 1-[Xtilde] 2 B 1 transitions. For NH2 the relative transition moments permit the calculation of the emission lifetimes (with the absolute value of the electronic transition moment taken from the ab initio calculations of Peyerimhoff and Buenker); the calculated lifetimes are found to agree very well with the experimental values of Halpern et al....

Orbital angular momentum in triatomic molecules

The photodissociation dynamics of A state ammonia molecules (both NH3 and ND3) has been further investigated using the technique of H(D) atom photofragment translational spectroscopy. The resulting NH2(ND2) fragments are observed to carry high levels of internal excitation, the precise disposition of which is sensitively dependent upon the parent v’2 level excited. Dissociation from the v2=0 level of the A state yields ground state NH2(ND2) fragments, primarily in their zero‐point level, but with high levels of rotational excitation specifically concentrated about the a‐inertial axis; the population distribution over the energetically accessible product rotational levels with N≂Ka appears near to statistical. In contrast, dissociation from the parent v’2=1 level yields a markedly inverted fragment internal energy distribution. These different energy disposals have been rationalized via classical trajectory calculations employing the best available ab initio potential energy surfaces for the A and X st...

State selective photodissociation dynamics of Ã state ammonia. II

ArF laser photodissociation of NH3 at 193 nm: internal energy distributions in NH2 X̃2B1 and Ã2A1, and two-photon generatin of NH A 3Π and b 1Σ+

Organic-inorganic perovskites are well suited for optoelectronic applications. In particular, perovskite single and perovskite tandem solar cells with silicon are close to their market entry. Despite their swift rise in efficiency to more than 21%, solar cell lifetimes are way below the needed 25 years. In fact, comparison of the time when the device performance has degraded to 80% of its initial value (T80 lifetime) of numerous solar cells throughout the literature reveals a strongly reduced stability under illumination. Herein, the various detrimental effects are discussed. Most notably, moisture- and heat-related degradation can be mitigated easily by now. Recently, however, several photoinduced degradation mechanisms have been observed. Under illumination, mixed perovskites tend to phase segregate, while, further, oxygen catalyzes deprotonation of the organic cations. Additionally, during illumination photogenerated charge can be trapped in the NH antibonding orbitals causing dissociation of the organic cation. On the other hand, organic-inorganic perovskites exhibit a high radiation hardness that is superior to crystalline silicon. Here, the proposed degradation mechanisms reported in the literature are thoroughly reviewed and the microscopic mechanisms and their implications for solar cells are discussed.

Influence of Radiation on the Properties and the Stability of Hybrid Perovskites.

Multiphoton-vacuum-ultraviolet laser photodissociation of acetylene: Emission from electronically excited fragments

Reactions of C2(a 3πu) with CH4, C2H2, C2H4, C2H6, and O2 using multiphoton UV excimer laser photolysis

Excited state dynamics and bimolecular quenching processes for NH2(Ã2A1)

Absolute rate constants are reported for reactions of C2O( X − 3Σ−) under pseudo-first-order decay conditions. C2O is generated by laser photodissociation of C3O2 at 266 nm, and detected by dye-laser induced fluorescence on the A − 3Πi- X − 3Σ− transition. Rate constants of (433 ± 12), (3.30 ± 0.12) and (1.12 ± 0.05) × 10−13 cm3 molecule−1 s−1 are reported for reactions with NO, O2 and isobutene. The NO value is approximate due to an apparent dark reaction between NO and C3O2. Upper limits of 1 × 10−14 cm3 molecule−1 s−1 are reported for reactions with H2, CO2, C3H2 and C2H4. The C2O + C3O2 reaction does not follow pseudo-first-order decay kinetics. Two explanations are proposed to explain this observation. Results are compared with previous relative rate measurements and are discussed in terms of their relevance to combustion chemistry.

V. M. Donnelly

Papers

ArF laser photodissociation of NH3 at 193 nm: internal energy distributions in NH2 X̃2B1 and Ã2A1, and two-photon generatin of NH A 3Π and b 1Σ+

Multiphoton-vacuum-ultraviolet laser photodissociation of acetylene: Emission from electronically excited fragments

Reactions of C2(a 3πu) with CH4, C2H2, C2H4, C2H6, and O2 using multiphoton UV excimer laser photolysis

Excited state dynamics and bimolecular quenching processes for NH2(Ã2A1)

C2O(X 3Σ−): absolute reaction rates measured by laser induced fluoresence