Molecular Photoionization and Photodetachment Cross Sections Based on L$$^2$$ Basis Sets: Theory and Selected Examples

By using the K-matrix technique for the continuum states that was previously employed with particularly diffuse L2 basis sets, it is shown that GTO bases are also capable of yielding accurate values for the properties belonging to the electronic continuum. The method has been tested for helium and proved of satisfactory accuracy also for the analysis of the autoionizing states. The results include the phase shifts of the continuum states of the 1Seand 1P° manifolds, the properties of the lowest resonances of these symmetries, the ground state photoionization cross section, and the S contribution to the 1s2p1P° photoionization cross section. The results obtained suggest that the proposed technique should be useful for computing molecular differential photoionization cross sections by exploiting the widely used codes that employ GTO bases. Keywords: photoionization, Gaussian basis sets, helium, autoionizing states.

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Molecular photoionization cross sections calculated by an effective plane wave method

Chemical Physics ◽

10.1016/0301-0104(76)80064-x ◽

1976 ◽

Vol 15 (3) ◽

pp. 345-361 ◽

Cited By ~ 13

Author(s):

P.R. Hilton ◽

S. Nordholm ◽

N.S. Hush

Keyword(s):

Plane Wave ◽

Cross Sections ◽

Wave Method ◽

Plane Wave Method ◽

Molecular Photoionization

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Molecular photoionization cross sections and asymmetry parameters by L2 basis functions calculations: H2O

The Journal of Chemical Physics ◽

10.1063/1.451391 ◽

1986 ◽

Vol 85 (12) ◽

pp. 7038-7045 ◽

Cited By ~ 55

Author(s):

I. Cacelli ◽

V. Carravetta ◽

R. Moccia

Keyword(s):

Cross Sections ◽

Basis Functions ◽

Molecular Photoionization ◽

Asymmetry Parameters

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Rotational de-excitation of tricarbon monosulfide (C3S) in collision with (He): potential energy surface and rates

Astrophysics and Space Science ◽

10.1007/s10509-020-03892-5 ◽

2020 ◽

Vol 365 (12) ◽

Author(s):

E. Sahnoun ◽

M. Ben Khalifa ◽

F. Khadri ◽

K. Hammami

Keyword(s):

Potential Energy ◽

Interstellar Medium ◽

Potential Energy Surface ◽

Cross Sections ◽

Energy Surface ◽

Accurate Determination ◽

Carbon Chain ◽

Basis Sets ◽

Rate Coefficients

AbstractDespite that the tricarbon monosulfide (C3S) is among the first sulfur-containing carbon-chain molecules to be detected in the interstellar medium, no studies focused on the determination of its collisional rates. These rate coefficients are essential to estimate the abundance of C3S in the interstellar medium. Computations of the C3S($^{1}\Sigma^{+}$ Σ + 1 ) downward rate coefficients, induced by collision with He, are performed by averaging the integral cross sections at low temperature (below $25~\text{K}$ 25 K ). Calculations of the cross sections in the close-coupling quantum time independent formalism for $E_{c}\leq110~\text{cm}^{-1}$ E c ≤ 110 cm − 1 and $J\leq10$ J ≤ 10 are based on a new 2-D potential energy surface. This PES is obtained from the explicit correlated coupled cluster with a single, double and perturbative triple excitation [ccsd(t)-f12] ab initio approach and the aug-cc-pVTZ basis sets. The PES have a global minimum of $-55.69~\text{cm}^{-1}$ − 55.69 cm − 1 located at $R=6.25$ R = 6.25 bohr and $\theta=94^{\circ}$ θ = 94 ∘ , and a second minimum of $-36.95~\text{cm}^{-1}$ − 36.95 cm − 1 at $R=9.35$ R = 9.35 bohr and $\theta=0^{\circ}$ θ = 0 ∘ . A comparison of C3S rates with those of the isoelectronic molecule C3O was made. The results indicate a great temperature dependence of the rates for transitions of $\Delta J>2$ Δ J > 2 . We expect that the new collisional data will allow for accurate determination of the C3S abundance in several interstellar regions.

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