Study On Polarization Spectrum Of Sm Atom Bound Highly Excited State In Electric Field

The study of rare-earth atoms in highly excited states is not only of great significance to disciplines such as astrophysics,quantum mechanics,atomic physics,and plasma physics,but also has significant application value in the development of new lasers and new energy sources.For Sm atom in rare-earth atoms,because the ground state has seven fine sub-levels 4f⁶6s²⁷F_0-6,and 8 valence electrons can be excited,resulting in extremely complex energy level structure,so its spectrum is more challenging than other rare-earth atoms.Previous studies on Sm atom have mostly focused on areas far below the first ionization threshold or auto-ionization energy domain,and studies on high-excitation states near the first ionization threshold are relatively less.This is mainly because for high-excitation states close to the first ionization threshold,the efficiency of photoionization detection is low,field ionization detection should be used,and multi-step resonance excitation is required,and the experiment is relatively complicated to implement.Based on the above factors,this paper systematically studies the highly excited states of Sm atoms in combination with polarization spectroscopy excitation.In order to confirm the applicability of polarization spectroscopy technology to complex Sm atoms,the two-color two-step resonance excitation technology and photoionization detection technology are used to study the spectrum of even-parity high excited states of Sm atom.Through two-step excitation,Sm atom is excited to even-parity excited state 4f⁶6s7s ⁷F_0,1,2,which is detected by photoionization detection technology.According to the principle of polarization selection,four kinds of polarization combination spectra,??,??,?⁺?⁺and?⁺?^-are compared and analyzed,and the total angular momentum quantum number J of three energy levels is determined.By changing the angle between the two-step linear polarization excited light vibration direction,the relationship between the signal strength and the angle is obtained,which further verifies the applicability of polarization spectrum technology to Sm atom.On this basis,the spectrum of odd parity Rydberg state of Sm atom is studied by three-color three-step resonance excitation technique and field ionization detection technique.By selecting two excitation paths of J from 0?1?0?1 and J from0?1?2?1,2,3,the Sm atom of odd parity Rydberg state with total angular momentum J=1 and J=1,2,3 is obtained.94 odd parity Rydberg energy levels have been found in the excitation path of J from 0?1?0?1.Three bound Rydberg series are determined by the change of effective quantum number and energy level.By fitting three Rydberg series,the ionization threshold of Sm atom is 45519.61 cm^-1.At the same time,the lifetime of these odd parity Rydberg states is determined by the delayed field ionization technique,and the relationship between the lifetime and the main quantum number n is analyzed.The effect of perturbed states on the lifetime is observed.In addition,the total angular momentum of these odd parity Rydberg states is further verified to be 1 by using six polarization combination excitations and polarization selection rules.In the excitation path of J from 0?1?0?1,2,3,the odd parity Rydberg states of Sm atom in the energy domain of 45277-45533 cm^-1 are systematically studied.The energy level positions and relative spectral line intensities of 116 highly excited Rydberg states are obtained,and the total angular momentum J is determined according to the polarization selection rule.Finally,by changing the intensity of the electrostatic field when Sm atom is excited,the variation of the first ionization threshold of Sm atom with the field intensity is studied.At the same time,by changing the polarization combination of the three-step laser,the position of the first ionization threshold of Sm atom in the zero field with different magnetic quantum numbers is accurately determined.first ionization threshold of Sm atom is 45519.69±0.17 cm^-1,which is consistent with the value obtained by the Rydberg series fitting.