Double ionization energies of HCl, HBr, Cl2 and Br2 molecules: An MRCI study

Efficient implementation of the single-reference algebraic diagrammatic construction theory for charged excitations: Applications to the TEMPO radical and DNA base pairs

We present an efficient implementation of the second- and third-order single-reference algebraic diagrammatic construction (ADC) theory for electron attachment and ionization energies and spectra [EA/IP-ADC(n), n = 2, 3]. Our new EA/IP-ADC program features spin adaptation for closed-shell systems, density fitting for efficient handling of the two-electron integral tensors, and vectorized and parallel implementation of tensor contractions. We demonstrate capabilities of our efficient implementation by applying the EA/IP-ADC(n) (n = 2, 3) methods to compute the photoelectron spectrum of the (2,2,6,6-tetramethylpiperidin-1-yl)oxyl (TEMPO) radical, as well as the vertical and adiabatic electron affinities of TEMPO and two DNA base pairs (guanine-cytosine and adenine-thymine). The spectra and electron affinities computed using large diffuse basis sets with up to 1028 molecular orbitals are found to be in good agreement with the best available results from the experiment and theoretical simulations.

Double and Triple Ionisation of Isocyanic Acid

Double and triple ionisation spectra of the reactive molecule isocyanic acid (HNCO) have been measured using multi-electron and ion coincidence techniques combined with synchrotron radiation and compared with high-level theoretical calculations. Vertical double ionisation at an energy of 32.8 ± 0.3 eV forms the ³A" ground state in which the HNCO²⁺ ion is long lived. The vertical triple ionisation energy is determined as 65 ± 1 eV. The core-valence double ionisation spectra resemble the valence photoelectron spectrum in form, and their main features can be understood on the basis of a simple and rather widely applicable Coulomb model based on the characteristics of the molecular orbitals from which electrons are removed. Characteristics of the most important dissociation channels are examined and discussed.

MRCI study on potential energy curves and spectroscopic properties of HF molecule

The potential energy curves of the low-lying electronic states of Hydrogen fluoride (HF) have been investigated by using multireference configuration interaction (MRCI) approach in combination with cc-pV5Z basis sets for H and aug-cc-pV6Z basis sets for F. Three singlet states (X(1)Σ(+),B(1)Σ(+), 1(1)Δ), two triplet valence states ((3)ΠV,(3)ΣV(+)) and five triplet Rydberg states ((3)ΣR1(+),(3)ΠR1,(3)ΔR1,(3)ΣR1(-),(3)ΠR2) of HF molecular are identified. (3)ΠV and (3)ΣV(+) states are repulsive, the spectroscopic parameters (De, Re, ωe, Be and Te) of the bound states are derived in the present work. We find that the order of energy levels of (3)ΣR1(+),(3)ΠR1,(3)ΔR1 electronic states is different with other literatures, (3)ΣR1(+) is the lowest in these three states, which undergoes a strongly avoided crossing with the valence state (3)ΣV(+). The (3)ΣR1(-) state is studied at the first time. In addition, the dipole moments (DM), transition dipole moments (TDM), Einstein coefficients (Av'v'') , Franck-Condon factors (qv'v'') and radiative lifetime (τv') for B(1)Σ(+)-X(1)Σ(+) systems are predicted.