Rb原子激发态碰撞能量转移

报道了用连续单模激光激发Rb原子至特定的激发态，从而观察激发态间的碰撞形成更高Rb原子激发态的实验结果.实验观察到Rb原子激发态的自发辐射与高激发态的碰撞形成通道之间的明显竞争，测得了高激发态的形成概率与激发光功率、原子蒸气温度及激光失谐的关系，所提出的碰撞能量转移机理较好地解释了实验结果. 关键词：     

钠原子第一激发态的非共振发射谱

一、引 言 这里的非共振发射谱是来源于碰撞引起的激发态精细结构之间的能量转移.对Na的第一激发态就是 Na(32P3/2)+X 　 Na(32P1/2)+X+　E(1)其中X是具有一定动能的碰撞原子,△E是3P态精细结构分裂能量。 精细结构之间的能量转移过程的研究不仅对于了解原子之间相互作用的机制有重要作用,而且很有实际意义.例如,最近Gelhwachs等人[1]把饱和光学非共振发射谱用于Na的单原子检测得到了相当好的结果. 我们利用Ar+激光泵浦的连续染料激光器对Na原子的D1,D2线分别进行选择性激发.观察了共振及非共振荧光.研究了它们随激发光强、Na原子密…     

Na(3P)+Na(3P)→Na(4F)+Na(3S)碰撞激发能量转移截面

利用激光(调离NaD_2线±20GHz)激发钠蒸汽,测量Na(3P)+Na(3P)→Na(4F)+Na(3S)的碰撞激发转移截面。因4F→3D的荧光位于红外(1.84μm),故检测3~2D_(3/2)→3~2P_(1/2)(818.3nm)和3~2D→3~2P_(3/2)(819.5nm)级联荧光信号。通过测量激光频率的Rayleigh散射光,直接D_2线荧光和敏化D_1线荧光分布,确定了钠原子密度,定出了有效辐射俘获衰变率Γ_(D_1)~e,Γ_(D_2)~e。结合激光功率吸收率的测量得到了Na(3P)的密度,从而给出转移截面σ(4F)=37A~2(±33％)。与其他作者的实验结果和理论值作了比较,进行了讨论。     

Rb(5PJ)+Rb(5PJ)→Rb(5S)+Rb(nl=5D,7S)碰撞能量合并

研究了Rb(5PJ) Rb(5PJ)→Rb(nlJ') Rb(5S)碰撞能量合并过程,利用单模半导体激光器分别共振激发Rb原子的5P1/2或5P3/2态,利用另一与泵浦激光束反向平行的单模激光束作为吸收线探测激发态原子密度及其空间分布,吸收线分别调至5P1/2→5D3/2和5P3/2→7S1/2跃迁.由激发态原子密度和谱线荧光比得到碰撞能量合并过程的截面,对5P3/2激发,碰撞转移得到5D5/2,5D3/2和7S1/2的截面分别是(1.32士0.59)×10-14,(1.18士0.53)×10-14和(3.21士1.44)×10-15cm2;对5P1/2激发,碰撞转移到5D5/2和5D3/2的截面分别是(6.57士2.96)×10-15和(5.90士2.66)×10-15cm2.与其他的实验结果进行了比较.     

Na原子能量自囚禁的加速效应

采用高分辨激光光谱方法，在较高温度条件下，实验观察到Na原子能量自囚禁加剧特征。出现原子加速的光谱行为；并导致零速度原子碰撞转移到高激发态的速度减少。从原子内能碰撞转移的角度，分析了原子速度分布变异的机理。     

Rb（5PJ）＋Rb（5PJ）→Rb（5JS）＋Rb（nl=5D，7S）碰撞能量合并

研究了Rb(5PJ)+Rb(5PJ)→Rb(nlJ')+Rb(5S)碰撞能量合并过程,利用单模半导体激光器分别共振激发Rb原子的5P1/2或5P3/2态,利用另一与泵浦激光束反向平行的单模激光束作为吸收线探测激发态原子密度及其空间分布,吸收线分别调至5P1/2→5D3/2和5P3/2→7S1/2跃迁.由激发态原子密度和谱线荧光比得到碰撞能量合并过程的截面,对5P3/2激发,碰撞转移得到5D5/2,5D3/2和7S1/2的截面分别是(1.32士0.59)×10-14,(1.18士0.53)×10-14和(3.21士1.44)×10-15cm2;对5P1/2激发,碰撞转移到5D5/2和5D3/2的截面分别是(6.57士2.96)×10-15和(5.90士2.66)×10-15cm2.与其他的实验结果进行了比较.     

夫兰克-赫兹实验中的气体击穿现象与空间电荷影响

实验采用充汞夫兰克-赫兹管(F-H管)测定汞的第一激发态(6~3P_1态)电位。当_电子在加速场中所获得的能量小于原子第一激发态的能量时,电子与原子的碰撞只能是弹性碰撞,根据理论计算,碰撞后电子损失的动能与原有动能的比值为δ=4mM/(m+M)~2cos~2θ=4r/(1+k)~2cos~2θ(1)式中k=M/m为原子与电子的质量比,因k》1, δ_max=4k/(1+k)~2=4/k→0即弹性碰撞时,电子几乎不损失能量。而当电子在加速场中所获得的能量等于或大于原子某一激发态的能量时,原子将被激发,这时碰撞为非弹性碰撞,据计算     

碰撞诱导钠分子 A~1Σ_u~ →Χ~1Σ_g~ 的荧光光谱

用532 0nm激光激发Na2分子到B1Πu电子态,记录了Na(3P)原子的跃迁和Na2分子的A1Σ u-Χ1Σ g的谱带。由Na与Na2激发态发射的光谱及其强度可以认定在Na-Na2系统中的碰撞过程,Na(3P)原子线是Na2(B1Πu)到Na(3P)的碰撞能量转移产生的,预解离过程也可产生原子线。而A1Σ u的辐射而引起的。在360℃,u-Χ1Σ g到A1Σ g谱带是由B1Πu到21Σ g的碰撞转移后再由21Σ 根据辐射衰变率和荧光强度,得到Na2(B1Πu)到Na2(21Σ g)碰撞转移率系数为7 1×10-10cm3s-1,而B1Πu的预解离率为2 3×106s-1。     

K(6S)+H2→K(4D)+H2的碰撞能量转移

激光双光子激发K原子至6s或4D态,测鼍了K(6S,4D)与H2的碰撞转移截面.池温在413K,H2气压在4～40 Pa范围内,K(6S,4D)-K的碰撞效应可略去.在激发6S态的情况下,记录6S→4P时间分辨荧光信号,从荧光强度的对数描绘出的直线斜率得到6S态的有效寿命,而4D态的布居随H2的增加而增加,因此引起4D→4P跃迁谱线的增强.在激发4D态的情况下,采用类似方法得到4D态的有效寿命,由Stern Volmet方程,测得6S和4D态的辐射寿命分别为(97±15)ns和(300±45)ns.激发态K原子总的碰撞去佰居截面为(1.6±0.3)×10-14cm2(对6S态)和(40±6)×10-16cm2(对4D态).该总截面中包含向K原子激发态的非反应碰撞转移截面以及与H2反应生成KH的反应截面.激发6S态,测量4D→4P的时间积分荧光强度随H2气压的变化,得到6S→4D的碰撞转移截面为(1.4±0.3)×10-14cm2.由此得到结论:K(6S)态主要是通过物理猝灭到K(4D)态,虽然在K(6S)+H2的碰撞中,观察到了由于化学反应生成的KH的存在.     

碰撞诱导钠分子A1Σ+u→X1Σ+g的荧光光谱

用532.0 nm激光激发Na2分子到B1Πu电子态,记录了Na(3P)原子的跃迁和Na2分子的A1Σ+u-Χ1Σ+g的谱带.由Na与Na2激发态发射的光谱及其强度可以认定在Na-Na2系统中的碰撞过程,Na(3P)原子线是Na2(B1Πu)到Na(3P)的碰撞能量转移产生的,预解离过程也可产生原子线.而A1Σ+u-Χ1Σ+g谱带是由B1Πu到21Σ+g的碰撞转移后再由21Σ+g到A1Σ+u的辐射而引起的.在360℃,根据辐射衰变率和荧光强度,得到Na2(B1Πu)到Na2(21Σ+g)碰撞转移率系数为7.1×10-10 cm3s-1,而B1Πu的预解离率为2.3×106 s-1.     

Excited nano-clusters

Received: 27 March 1998     

Excited levels of Pa

The -decay spectrum of ²³⁷Np was measured with a semiconductor spectrometer of 18 keV effective resolution (FWHM). Over 13 new lines were identified. The γ-ray spectrum of ²³⁷Np and ²³³Th from 20 to 1000 keV was studied with high-resolution Ge(Li) and Si(Li) detectors. From these data and previous results, a more complete level scheme of ²³³Pa is constructed.

Nilsson assignments for rotational bands based on levels at 0, 86.6 and 237.7 keV are confirmed. A new band whose lowest member is the level at 170.3 keV is identified and new levels with probable vibrational character are studied.     

Excited States of Magnetotrion

New lines are observed in the photoluminescence spectrum of a two-dimensional electron gas in a quantizing magnetic field at a filling factor of ν = 2 upon the photoexcitation of a nonequilibrium ensemble of cyclotron magnetoexcitons. Their energies lie in the region forbidden for single-particle optical transitions and allowed for inner transitions from excited states of three-particle translationally invariant complexes called magnetotrions. It is suggested that the new lines are associated with the complicated spectrum of internal motion in the magnetotrion, composed of an electron at the first Landau level and two identical holes at the zeroth Landau level.     

Excited states of HCl

Ab initio CI calculations are presented for potential curves for the valence states of HCl, for the vertical electronic spectrum and for the potential curve for the B ¹Σ⁺ state. The valence ¹Π, ³Π and ³Σ⁺ states are found to be repulsive. Calculated vertical excitation energies are in good agreement with experiment. The B ¹Σ⁺ curve is predicted to have a double minimum.     

Excited states of hypernuclei

A two-body model of a hypernucleus with realistic N potentials is used to calculate the energies of the excited states of the particle in heavy hypernuclei. The positions of the levels are investigated as functions of: a) the form of the N potential, b) the size of the core nucleus and the form of the nucleon density, and c) the mass number A.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 4, pp. 33–37, April, 1980.     

Excited states in 130Ba

Excited states of ¹³⁰Ba have been studied by means of in-beam γ-ray spectroscopy and electron-spectroscopy via the reaction ¹²⁰Sn(¹³C, 3n). Spin and parity assignments have been made for 28 new levels. A comparison with a cranking-model calculation shows that the negative-parity band based on the 5^? state is a two-quasiproton band.     

Excited states of confined quarks

Low lying excitations of colored quarks and gluons are studied in the bag theory. The baryons and mesons considered have one quark in a P-wave excited state and the remainder in the ground state. They correspond to 1/2⁻ and 3/2⁻ baryons and to 0⁺ and 1⁺ mesons. Gluon hyperfine interactions are included to lowest order. SU(3) is broken by the strange quark mass. All parameters of the model were determined previously by fitting the masses of the light hadrons. The calculated masses of these states are generally found to be lighter than the observed states. Our spectrum contains states which do not occur in models of quark confinement with only two body forces but which should be present in the physical spectrum of any baglike confinement model.