Benchmark calculations of the 1D Rydberg spectrum of beryllium

High-accuracy calculations are performed on the 1D spectrum of beryllium with the use of all-electron explicitly correlated Gaussian (ECG) functions. In the first step, a nonrelativistic wave function is generated for each state with the ECG nonlinear parameters variationally optimized using a procedure employing energy gradient determined with respect to these parameters. The wave functions are used to calculate the leading relativistic corrections employing the recently implemented algorithms. The state total energies and the interstate transition energies are compared with the high-quality experimental results.