AMPL Database

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Atomic and molecular Group, AMPL

The group investigates electron, positron, and photon-induced studies of relevant atoms and compounds. Many environments have abundant free electrons/positrons/photons to interact with atoms/molecules, making these processes simple. Advanced radio-astronomical equipment have detected atomic, molecular, and ionic species in the interstellar medium, enriching the database. This'molecular hunting' has found more than 200 species. These compounds' interactions with electrons/positrons/photons underpin the physics and local chemistry of these media and help explain the universe's origin. Plasmas, controlled thin film deposition, and biological systems are similar. Quantum mechanical theories are used to compute intermediate to high energy electron/positron impact elastic and inelastic (electronic excitations, ionization, and positronium production) cross sections and photoionization.

Atomic and molecular data

The targets studied by our group, AMPL, are listed below for each projectile and cross section type. The link will provide you with the published paper. The data is available with the authors and if needed please contact at the email id given below.

Electron collision

Total cross section (Qtot)

We have utilized the optical potential method [Phys. Rev. A: 88 (2013) 32707], and R-mattix method [J. Phys. Chem. A 124 (2020) 3581−3589] to compute the electron impact integral cross section over a wide energy range. The total cross section referred to here includes total elastic, total ionization, and total electronic excitations for all dipole allowed transitions.

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Total elastic cross section (Qel)

The optical potential approach [Phys. Rev. A: 88 (2013) 32707] and the R-matrix method [J. Phys. Chem. A 124 (2020) 3581−3589] were employed to calculate the integral elastic cross section for electron impact over a broad range of energies.

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Total ionization cross section (Qion)

The optical potential approach [Phys. Rev. A: 88 (2013) 32707] calculates the electron impact integral inelastic cross section, which includes both ionization and excitation channels. The total ionization cross section is then calculated using the semi-classical CSP-ic method [J. Phys. Chem. A 127 (2023) 5414-5423] from the inelastic cross section. These calculations are performed for electron energies from the molecule's ionization threshold, up to 5000 eV.

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Positron collision

Total elastic cross section (Qel)

The optical potential method for electron scattering has been suitably modified to compute positron interactions with atoms and molecules. This modified SCOP method [Chem. Phys. Lett. 692 (2018) 242-248] is used to calculate the elastic cross section. These calculations are performed for positrons with energies from the molecule's positronium formation threshold and to 5000 eV.

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Direct ionization cross section (Qion)

We have appropriately modified the optical potential approach for electron scattering to calculate positron interactions with atoms and molecules. The modified SCOP method [Chem. Phys. Lett. 692 (2018) 242-248] calculates the inelastic cross section, which we then use to evaluate the total ionization cross section using the CSP-ic method. We perform these calculations for positron energies, starting from the molecule's positronium formation threshold and going up to 5000 eV.

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Positron formation cross section (Qpos)

The modified optical potential technique is used to determine the inelastic cross sections both with and without the positronium formation channel [Chem. Phys. Lett. 692 (2018) 242-248]. Afterwards, we compute the total cross section for positronium formation by subtracting these. These calculations are performed in the energy range from the molecule's positronium generation threshold to about 200 eV, since the positronium creation channel becomes negligible above 200 eV.

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Total ionization cross section (Qtion)

The total ionization cross section is the sum of direct ionization cross section + positronium formation cross section.

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Photoionization