Oscillator Strengths for the Helium Isoelectronic Sequence

Area of Science:

• Atomic Physics
• Quantum Chemistry

Background:

• Helium isoelectronic sequence ions are fundamental systems for testing quantum mechanical theories.
• Accurate calculations of atomic properties are crucial for understanding atomic structure and spectra.

Purpose of the Study:

• To compute variational wavefunctions and oscillator strengths for various terms of helium isoelectronic sequence ions.
• To assess the reliability of these calculations through internal consistency and comparison with existing data.

Main Methods:

• Employed Hylleraas-type trial functions with explicit dependence on interelectronic distance (r12).
• Utilized expansion lengths of approximately 50 terms for variational wavefunctions.
• Calculated oscillator strengths using both dipole length and dipole velocity formulas for allowed transitions.

Main Results:

• Computed variational wavefunctions for 1S, 2S, 2P, 3P, and 3D terms across the helium isoelectronic sequence (He to Ne+8).
• Obtained oscillator strengths for all allowed transitions, showing good agreement between length and velocity formulations.
• Achieved high accuracy in computed energies, indicating reliable wavefunction results.

Conclusions:

• The computed wavefunctions and oscillator strengths are highly reliable for the helium isoelectronic sequence.
• The accuracy is estimated to be around 5 percent or better, supported by energy calculations and inter-formula agreement.
• These results provide valuable data for further theoretical and experimental studies in atomic physics.