{"title":"Mechanism of metastable krypton atom preparation via laser-induced ionization","authors":"","doi":"10.1016/j.jqsrt.2024.109233","DOIUrl":null,"url":null,"abstract":"<div><div>Preparation of metastable Kr atoms in the 5s[3/2]<sub>2</sub> level via laser-induced ionization has been achieved. The temporal evolution of the intensity of Kr atomic spectral lines at 760.15 nm, 811.29 nm, and 431.96 nm was used to elucidate the production mechanisms of metastable Kr atoms. These mechanisms primarily involve two processes: the “excitation + radiation” process, dominated by multiphoton excitation and initial plasma-induced electron impact excitation, and the “ion-electron recombination” process, governed by avalanche ionization. The decay time constants of Kr atomic spectral lines, corresponding to the “excitation + radiation” and “ion-electron recombination” processes respectively, were obtained experimentally under both strong and weak ionization conditions. The experiments revealed delay in preparations of metastable Kr atoms between these two processes. To reduce the loss of metastable Kr atoms and effectively utilize their peak concentration, we drew inspiration from metastable rare gas lasers and proposed the “cycling” idea to keep metastable Kr atoms produced by these two processes as synchronized as possible. We used 811.29 nm laser to excite metastable Kr atoms generated rapidly during the “excitation + radiation” stage to the 5p[5/2]<sub>3</sub> level. The Kr atoms returned to the 5s[3/2]<sub>2</sub> level through spontaneous radiation, merging with metastable Kr atoms that were slowly produced during the “ion-electron recombination” stage. We hope that the “cycling” idea can shorten the delay in preparations of metastable Kr atoms from both processes and enhance the peak concentration of metastable Kr atoms. However, the experimental results didn't meet expectations, as we observed a decrease in the 811.29 nm fluorescence after laser excitation, attributed to the accumulation of 5p[5/2]<sub>3</sub> level Kr atoms. These atoms undergo energy pooling to populate the 4d’[3/2]<sub>1</sub> and 5d[7/2]<sub>3</sub> levels, followed by absorption of 811.29 nm laser energy leading to photoionization. Reducing the concentration of 5p[5/2]<sub>3</sub> level Kr atoms helps mitigate the reionization issue.</div></div>","PeriodicalId":16935,"journal":{"name":"Journal of Quantitative Spectroscopy & Radiative Transfer","volume":null,"pages":null},"PeriodicalIF":2.3000,"publicationDate":"2024-10-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Journal of Quantitative Spectroscopy & Radiative Transfer","FirstCategoryId":"101","ListUrlMain":"https://www.sciencedirect.com/science/article/pii/S0022407324003406","RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q2","JCRName":"OPTICS","Score":null,"Total":0}
引用次数: 0
Abstract
Preparation of metastable Kr atoms in the 5s[3/2]2 level via laser-induced ionization has been achieved. The temporal evolution of the intensity of Kr atomic spectral lines at 760.15 nm, 811.29 nm, and 431.96 nm was used to elucidate the production mechanisms of metastable Kr atoms. These mechanisms primarily involve two processes: the “excitation + radiation” process, dominated by multiphoton excitation and initial plasma-induced electron impact excitation, and the “ion-electron recombination” process, governed by avalanche ionization. The decay time constants of Kr atomic spectral lines, corresponding to the “excitation + radiation” and “ion-electron recombination” processes respectively, were obtained experimentally under both strong and weak ionization conditions. The experiments revealed delay in preparations of metastable Kr atoms between these two processes. To reduce the loss of metastable Kr atoms and effectively utilize their peak concentration, we drew inspiration from metastable rare gas lasers and proposed the “cycling” idea to keep metastable Kr atoms produced by these two processes as synchronized as possible. We used 811.29 nm laser to excite metastable Kr atoms generated rapidly during the “excitation + radiation” stage to the 5p[5/2]3 level. The Kr atoms returned to the 5s[3/2]2 level through spontaneous radiation, merging with metastable Kr atoms that were slowly produced during the “ion-electron recombination” stage. We hope that the “cycling” idea can shorten the delay in preparations of metastable Kr atoms from both processes and enhance the peak concentration of metastable Kr atoms. However, the experimental results didn't meet expectations, as we observed a decrease in the 811.29 nm fluorescence after laser excitation, attributed to the accumulation of 5p[5/2]3 level Kr atoms. These atoms undergo energy pooling to populate the 4d’[3/2]1 and 5d[7/2]3 levels, followed by absorption of 811.29 nm laser energy leading to photoionization. Reducing the concentration of 5p[5/2]3 level Kr atoms helps mitigate the reionization issue.
期刊介绍:
Papers with the following subject areas are suitable for publication in the Journal of Quantitative Spectroscopy and Radiative Transfer:
- Theoretical and experimental aspects of the spectra of atoms, molecules, ions, and plasmas.
- Spectral lineshape studies including models and computational algorithms.
- Atmospheric spectroscopy.
- Theoretical and experimental aspects of light scattering.
- Application of light scattering in particle characterization and remote sensing.
- Application of light scattering in biological sciences and medicine.
- Radiative transfer in absorbing, emitting, and scattering media.
- Radiative transfer in stochastic media.