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

One of the most significant developments in computational atomic and molecular physics in recent years has been the introduction of B-spline basis sets in calculations of atomic and molecular structure and dynamics. B-splines were introduced in applied mathematics more than 50 years ago, but it has been in the 1990s, with the advent of powerful computers, that the number of applications has grown exponentially. In this review we present the main properties of B-splines and discuss why they are useful to solve different problems in atomic and molecular physics. We provide an extensive reference list of theoretical works that have made use of B-spline basis sets up to 2000. Among these, we have focused on those applications that have led to the discovery of new interesting phenomena and pointed out the reasons behind the success of the approach.

https://iopscience.iop.org/article/10.1088/0034-4885/64/12/205/pdf

Applications of B-splines in atomic and molecular physics

A new collection of photodissociation and photoionisation cross sections for 102 atoms and molecules of astrochemical interest has been assembled, along with a brief review of the basic physical processes involved. These have been used to calculate dissociation and ionisation rates, with uncertainties, in a standard ultraviolet interstellar radiation field (ISRF) and for other wavelength-dependent radiation fields, including cool stellar and solar radiation, Lyman-α dominated radiation, and a cosmic-ray induced ultraviolet flux. The new ISRF rates generally agree within 30% with our previous compilations, with a few notable exceptions. Comparison with other databases such as PHIDRATES is made. The reduction of rates in shielded regions was calculated as a function of dust, molecular and atomic hydrogen, atomic C, and self-shielding column densities. The relative importance of these shielding types depends on the atom or molecule in question and the assumed dust optical properties. All of the new data are publicly available from the Leiden photodissociation and ionisation database. Sensitivity of the calculated rates to variation of temperature and isotope, and uncertainties in measured or calculated cross sections, are tested and discussed. Tests were conducted on the new rates with an interstellar-cloud chemical model, and find general agreement (within a factor of two) in abundances obtained with the previous iteration of the Leiden database assuming an ISRF, and order-of-magnitude variations assuming various kinds of stellar radiation. The newly parameterised dust-shielding factors makes a factor-of-two difference to many atomic and molecular abundances relative to parameters currently in the UDfA and KIDA astrochemical reaction databases. The newly-calculated cosmic-ray induced photodissociation and ionisation rates differ from current standard values up to a factor of 5. Under high temperature and cosmic-ray-flux conditions the new rates alter the equilibrium abundances of abundant dark cloud abundances by up to a factor of two. The partial cross sections for H2 O and NH3 photodissociation forming OH, O, NH2 and NH are also evaluated and lead to radiation-field-dependent branching ratios.

/pdf/photodissociation-and-photoionisation-of-atoms-and-molecules-1bnk2a3c2i.pdf

Photodissociation and photoionisation of atoms and molecules of astrophysical interest

A model based upon Viking data is constructed of the Martian atmosphere, and a comprehensive quantitative discussion is given of the measurements of the ultraviolet dayglow. A detailed assessment is made of the heating of the neutral and ionized components of the atmosphere arising from the absorption of ultraviolet solar radiation.

/pdf/ionization-luminosity-and-heating-of-the-upper-atmosphere-of-1hvc1zxtwr.pdf

Ionization, luminosity, and heating of the upper atmosphere of Mars

Photoionization cross sections for reaction intermediates in hydrocarbon combustion

The absorption cross sections of N2, O2, CO, NO, CO2, N2O, CH4, C2H4, C2H6, C4H10 have been measured photoelectrically in the 180–700 A region using synchrotron radiation. The absorption cross sections in the region λ ≥ 500 A was found to be structureless and to increase monotonically with wavelength for all gases. The positions of the structure observed in the 520–720 A region for N2, O2, CO2 and N2O are consistent with the various Rydberg series reported by previous authors.

The absorption cross sections of N2, O2, CO, NO, CO2, N2O, CH4, C2H4, C2H6 and C4H10 from 180 to 700Å

Using synchrotron radiation as a continuum light source, the photoabsorption and photoionization cross sections of NH3, PH3, H2S, C2H2, and C2H4 have been measured from their respective ionization thresholds to 1060 A. The vibrational constants associated with the nu(2) totally symmetric, out-of-plane bending vibration of the ground electronic state of PH3(+) have been obtained. The cross sections and quantum yields for producing neutral products through photoexcitation of these molecules in the given spectral regions have also been determined. In the present work, autoionization processes were found to be less important than dissociation and predissociation processes in NH3, PH3, and C2H4. Several experimental techniques have been employed in order to examine the various possible systematic errors critically.

Photoabsorption and photoionization cross sections of NH3, PH3, H2S, C2H2, and C2H4 in the VUV region

The absolute photoabsorption cross sections of H2 and D2 have been measured photoelectrically in the wavelength region from 180 to 780 A using synchrotron radiation. At photon wavelengths shorter than 650 A, the absorption cross section was found to be structureless and to decrease montonically with decreasing wavelength. In this spectral region, both gases have nearly equal absorption cross sections, varying only within the experimental error. At photon wavelengths greater than λ 650 A, structure is evident in the cross section of both gases and presumably corresponds to the Rydberg States reported by various authors.

The absorption cross sections of H2 and D2 from 180 to 780 Å

Absolute photoabsorption cross sections for H 2 O and D 2 O have been measured photoelectrically from λλ 180 to 790 A using synchrotron radiation. The cross sections increase smoothly with wavelength to ∼λ610 A, with both H 2 O and D 2 O displaying a broad absorption band extending above a nearly linear background from λλ 400 to 490 A. The continuum has a maximum of ∼ 22.5 Mb at λ 640 A. Above λ 615 A, superimposed on the continuum, a diffuse structure appears which is similar to the vibrational structure of the 2 B 2 states of H 2 O + and D 2 O + as observed in photoelectron spectra. The structure is believed to arise from excitation of a 1 b 2 electron to the vibrational levels of a Rydberg orbital with n ∗ ≈ 2.64.

D.L. Judge

Papers

The absorption cross sections of N2, O2, CO, NO, CO2, N2O, CH4, C2H4, C2H6 and C4H10 from 180 to 700Å

Photoabsorption and photoionization cross sections of NH3, PH3, H2S, C2H2, and C2H4 in the VUV region

The absorption cross sections of H2 and D2 from 180 to 780 Å

Absolute photoabsorption cross sections for H2O and D2O from lambda 180-790 A