A method to describe the generation channels of high-order harmonics is proposed. According to this method, the mechanism of generation-channel interference of high-order harmonics is revealed clearly. We take the anharmonic oscillator driven by bi-chrome fields as an example to illustrate that this method can be used to understand the effect of generation-channel interference.
The 1^10^＋ 1^1（-1）^＋and 1^1（2）^＋ states of the helium atom in the magnetic field regime between 0 and 100 a.u. are studied using a full configuration-interaction （CI） approach. The total energies, derivatives of the total energy with respect to the magnetic field and ionisation energies are calculated with Hylleraas-like functions in spherical coordinates in low to intermediate fields and Hylleraas Caussian functions in cylindrical coordinates in intermediate to high fields, respectively. In intermediate fields, the total energies and ionisation energies are determined in terms of Hermite interpolation, based on the results obtained with the two above-mentioned basis functions. Calculations show that the current method can produce lower total energies and larger ionisation energies, and make the two ionisation energy curves obtained with the two above-mentioned basis functions join smoothly in intermediate fields. Comparisons are also made with previous works.
Using a full configuration-interaction method with Hylleraas-Gaussian basis function, this paper investigates the 1^10^＋, 1^1（-1）^＋ and 1^1（-2）6＋ states of the hydrogen negative ion in strong magnetic fields. The total energies, electron detachment energies and derivatives of the total energy with respect to the magnetic field are presented as functions of magnetic field over a wide range of field strengths. Compared with the available theoretical data, the accuracy for the energies is enhanced significantly. The field regimes 3 〈 γ 〈 4 and 0.02 〈 γ 〈 0.05, in which the 1^1（-1）6＋ and 1^1（-2）^＋ states start to become bound, respectively, are also determined based on the calculated electron detachment energies.
We calculated the power spectra of harmonic generation for the one-electron system in 7 potential models with different quantities of bound states. It indicates that the increase of weakly bound states has little influence on the enhancement of harmonic intensity in the high-order region. Further research on the so-called channel-interference of harmonic generation is obtained, which shows that the channel-interference of harmonic generation exists for all potential models. Therefore, channel-interference maybe a ubiquitous phenomenon for one-electron system driven by bichromatic field, and the increase of bound states can augment the effect of channel-interference. Our calculations can provide some insight on the mechanism of channel-interference and harmonic generation.
