High-harmonic-generation spectra of HCN: A time-dependent density-functional-theory study

This study examines the high-harmonic-generation spectra of hydrogen cyanide, focusing on the contrast between even and odd harmonics and their emissions under two opposite laser-molecule orientations. At lower energies, the emissions are higher when the potential energy of the hydrogen side is lowered, while at higher energies, the emissions are more pronounced when the potential energy of the nitrogen side is reduced. When the laser polarization aligns parallel to the molecular axis, the combined contributions of the σ and π orbitals result in a two-electron process, leading to varied intensity ratios between even and odd harmonics that a single active electron model cannot adequately explain.