湖泊沉积物氮同位素(δ^(15)N)在古环境、古气候变化方面有着指示气候干湿变化的重要作用,但目前学界对于δ^(15)N记录作为气候代用指标所指示的气候干湿变化特征仍缺乏深入探索。本文以贵州省梵净山九龙池湖泊沉积物为研究对象,分析并...湖泊沉积物氮同位素(δ^(15)N)在古环境、古气候变化方面有着指示气候干湿变化的重要作用,但目前学界对于δ^(15)N记录作为气候代用指标所指示的气候干湿变化特征仍缺乏深入探索。本文以贵州省梵净山九龙池湖泊沉积物为研究对象,分析并探讨δ^(15)N所记录的梵净山地区气候干湿变化过程与特征,并结合总有机碳(TOC)、总氮(TN)和碳氮比值(C/N)数据进行对比研究,结果表明:(1)由于九龙池湖泊沉积物有机质受流域输入影响,气候湿润时,陆生植物增多,土壤湿度增大,外源输入对湖泊沉积物有机质影响增大,沉积物δ^(15)N值偏负;气候干旱时,陆生植物减少,土壤湿度降低,外源输入对湖泊沉积物有机质影响减小,沉积物δ^(15)N值偏正;(2)九龙池湖泊沉积物δ^(15)N记录很好地揭示了梵净山地区全新世的气候干湿变化过程,即早期(11.5—9.2 ka B.P.)亚洲夏季风增强,气候从干旱期向湿润期转变,中期(9.2—3.0 ka B.P.)亚洲夏季风强盛,气候整体处于湿润期,晚期(3.0—2.2 ka B.P.)亚洲夏季风减弱,气候由湿润期向干旱期方向发展。该记录与中国西南地区其他气候代用指标所记录的全新世气候变化具有区域一致性,但在部分时段有明显差异,说明西南地区气候和环境演变即响应了全球性变化又有区域特征。本研究表明,九龙池湖泊沉积物δ^(15)N记录可用于揭示研究区域全新世气候与环境变化的特征,是一种具有实用价值的古气候代用记录。展开更多
A^(6)Li(^(16)O,^(19)Ne^(∗))^(3)H multi-nucleon transfer-reaction experiment was performed to populate the highly excited states in^(19)Ne.The subsequent decay particles,^(4)He or protons from the^(19)Ne resonant state...A^(6)Li(^(16)O,^(19)Ne^(∗))^(3)H multi-nucleon transfer-reaction experiment was performed to populate the highly excited states in^(19)Ne.The subsequent decay particles,^(4)He or protons from the^(19)Ne resonant states,were detected in coincidence with the recoil 3 H.The excitation-energy spectra of^(19)Ne were reconstructed using the detected proton or^(4)He and the deduced^(18)F or^(15)O data,respectively.A broad resonance at about 7.85 MeV(1/2^(+))was observed,with partial decay widths different from the previously reported values,which may have a significant impact on the destruction of 18 F in astrophysical processes.Several resonances up to very high excitation energies have been identified with a largeα-clustering strength,which confirm the formation of the cluster structure with a one-hole configuration in light nuclei and encourage further systematic studies of the cluster structure in^(19)Ne.展开更多
A transfer reaction and cluster-decay experiment,12C(16O,24Mg→ α+20Ne)α, was performed at a beam energy of 96 MeV. Both recoil and decay α particles were detected in coincidence, allowing us to deduce the energymo...A transfer reaction and cluster-decay experiment,12C(16O,24Mg→ α+20Ne)α, was performed at a beam energy of 96 MeV. Both recoil and decay α particles were detected in coincidence, allowing us to deduce the energymomentum of a20Ne fragment. A number of resonant states of24Mg were reconstructed up to an excitation energy of approximately 30 MeV. Owing to the experimentally achieved excellent resolutions of the Q-value and excitationenergy spectra, the relative decay widths for each resonant state in24Mg to various final states of20Ne were extracted, along with the total decay width. The obtained results provide good testing ground for theoretical descriptions of multiple clustering configurations in24Mg.展开更多
文摘湖泊沉积物氮同位素(δ^(15)N)在古环境、古气候变化方面有着指示气候干湿变化的重要作用,但目前学界对于δ^(15)N记录作为气候代用指标所指示的气候干湿变化特征仍缺乏深入探索。本文以贵州省梵净山九龙池湖泊沉积物为研究对象,分析并探讨δ^(15)N所记录的梵净山地区气候干湿变化过程与特征,并结合总有机碳(TOC)、总氮(TN)和碳氮比值(C/N)数据进行对比研究,结果表明:(1)由于九龙池湖泊沉积物有机质受流域输入影响,气候湿润时,陆生植物增多,土壤湿度增大,外源输入对湖泊沉积物有机质影响增大,沉积物δ^(15)N值偏负;气候干旱时,陆生植物减少,土壤湿度降低,外源输入对湖泊沉积物有机质影响减小,沉积物δ^(15)N值偏正;(2)九龙池湖泊沉积物δ^(15)N记录很好地揭示了梵净山地区全新世的气候干湿变化过程,即早期(11.5—9.2 ka B.P.)亚洲夏季风增强,气候从干旱期向湿润期转变,中期(9.2—3.0 ka B.P.)亚洲夏季风强盛,气候整体处于湿润期,晚期(3.0—2.2 ka B.P.)亚洲夏季风减弱,气候由湿润期向干旱期方向发展。该记录与中国西南地区其他气候代用指标所记录的全新世气候变化具有区域一致性,但在部分时段有明显差异,说明西南地区气候和环境演变即响应了全球性变化又有区域特征。本研究表明,九龙池湖泊沉积物δ^(15)N记录可用于揭示研究区域全新世气候与环境变化的特征,是一种具有实用价值的古气候代用记录。
基金Supported by the National Key R&D Program of China(2018YFA0404403,2022YFA1602302)the National Natural Science Foundation of China(11875074,11875073,12235020,12027809,11961141003,U1967201,U2167204,11775004,11775003)+2 种基金the Continuous Basic Scientific Research Project(WDJC-2019-13)the State Key Laboratory of Nuclear Physics and Technology,Peking University(NPT2020KFY10)the Leading Innovation Project(LC192209000701,LC202309000201)。
文摘A^(6)Li(^(16)O,^(19)Ne^(∗))^(3)H multi-nucleon transfer-reaction experiment was performed to populate the highly excited states in^(19)Ne.The subsequent decay particles,^(4)He or protons from the^(19)Ne resonant states,were detected in coincidence with the recoil 3 H.The excitation-energy spectra of^(19)Ne were reconstructed using the detected proton or^(4)He and the deduced^(18)F or^(15)O data,respectively.A broad resonance at about 7.85 MeV(1/2^(+))was observed,with partial decay widths different from the previously reported values,which may have a significant impact on the destruction of 18 F in astrophysical processes.Several resonances up to very high excitation energies have been identified with a largeα-clustering strength,which confirm the formation of the cluster structure with a one-hole configuration in light nuclei and encourage further systematic studies of the cluster structure in^(19)Ne.
基金Supported by the National Key R&D Program of China (2018YFA0404403)the National Natural Science Foundation of China (11875074, 11875073, 12027809,11961141003, U1967201, 11775004, and 11775003)+1 种基金the Continuous Basic Scientific Research Project (WDJC-2019-13)the State Key Laboratory of Nuclear Physics and Technology,Peking University (NPT2020KFY10)。
文摘A transfer reaction and cluster-decay experiment,12C(16O,24Mg→ α+20Ne)α, was performed at a beam energy of 96 MeV. Both recoil and decay α particles were detected in coincidence, allowing us to deduce the energymomentum of a20Ne fragment. A number of resonant states of24Mg were reconstructed up to an excitation energy of approximately 30 MeV. Owing to the experimentally achieved excellent resolutions of the Q-value and excitationenergy spectra, the relative decay widths for each resonant state in24Mg to various final states of20Ne were extracted, along with the total decay width. The obtained results provide good testing ground for theoretical descriptions of multiple clustering configurations in24Mg.
