Rb(7D)+Na(3S)碰撞激发转移过程

研究了Rb Na异核系统的能量碰撞合并逆过程 (REP)。两步激发Rb原子到 7D3 / 2 态。应用双调制技术探测Na(3Pj)原子发射的荧光 ,基态Na原子密度用光学吸收方法测量。得到了REP率系数 ,讨论了其他过程对率系数的影响。     

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.     

碰撞能量转移Cs(6P)+Cs(5D)→Cs(6S)+Cs(nL=9S,5F)的截面测量

二步激发Cs原子至8S态,测量了碰撞转移过程Cs(6P)+Cs(5D)→Cs(6S)+Cs(nL=9S,5F)的截面,测量由7D,9S和5F态发射的荧光强度,从荧光强度比和σ(7D)值得到了σ(9S)和σ(5F),而σ(7D)已经进行过绝对测量,截面值σ(9S)和σ(5F)分别为8.7×10-15和1.3×10-14?cm2.讨论了能量转移过程9S+6S5F+6S对σ(9S)和σ(5F)的影响.     

激发态Cs原子间碰撞能量转移截面

在Cs蒸气密度为1013?cm-3量级范围内,研究了6P3/2+6P3/2→6DJ+6S碰撞能量合并过程.利用单模半导体激光器共振激发6P3/2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,吸收线调至6P3/2→8S1/2跃迁,并可平行于泵浦激光束移动.由激发态原子密度和谱线的荧光强度比得到碰撞能量合并的截面.碰撞转移到6D5/2和6D3/2的截面分别是(4.1±1.8)×10-15和(2.2±1.0)×10-15?cm2.与其它实验结果进行了比较.     

Na(4D)+Na(3S)Na(4F)+Na(3S)碰撞能量转移截面

利用双光子吸收,将Na(3S)原子激发到4D态,测量了Na(4D)+Na(3S)Na(4F)+Na(3S)碰撞能量转移截面,因为直接由4F→3D的荧光不能探测,所以检测3D→3P级联荧光讯号。结合基态钠原子密度的测量,给出了截面值σ_4D→4F=1.3 x 10~(-14)±28％(cm~2)。     

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。     

激发态Na和K原子间的碰撞能量合并

置于同一池中的Ｎａ原子和Ｋ原子，分别被连续染料激光器和Ｋ光谱灯激发型Ｎａ（３Ｐ），Ｋ（４Ｐ），Ｎａ（３Ｐ）原子密度由吸收等效宽度技术测定。利用调制技术，分离出了由异核碰撞产生的荧光光谱，观察到了Ｎａ（３Ｐ）和Ｋ（４Ｐ）间的磁能量合并现象，并测定了其碰撞截面。     

Na（3P）十Rb（5P）碰撞能量转移截面

置于同一池中的钠原子和铷原子，分别被连续染料激光器和铷光谱灯激发到Ｎａ（３Ｐ），Ｒｂ（５Ｐ），Ｎａ（３Ｐ）原子密度由吸收等效宽度技术测定，利用调制技术分离出了由异核碰撞产生的荧光光谱，观察到了Ｎａ（３Ｐ）和Ｒｂ（５Ｐ）问的碰撞能量合并现象，并测定了其碰撞截面。     

Cs(8S -4F)-Ar，H2的碰撞能量转移

利用脉冲激光器双光子激发Cs-H2（或Ar）样品池中的Cs原子至8S态,研究了Cs(8S)+M→Cs(4F)+M ,(M= H2,Ar)碰撞能量转移和Cs(4F)+H2→CsH+H反应过程,建立了二能级模型的速率方程组。在不同的Ar密度下测量直接8S→6P与敏化4F→5D积分荧光强度比,得到8S→4F转移速率系数5.3×10-12cm3s-1和4F态的猝灭速率系数4.4×10-13cm3s-1。用相同的方法测得Cs－H2中8S→4F的转移速率系数为1.0×10-9cm3s-1,而4F态的猝灭速率系数1.3×10-10cm3s-1比Cs－Ar中大得多,它是反应与非反应速率系数之和。利用实验数据确定非反应速率系数为8.3×10-11cm3s-1,得出Cs（4F）与H2的反应截面为(2.0±0.8)×10-16cm3s-1。与已有的其它实验结果比较,Cs各激发态与H2的反应活动性顺序为7P>4F>6D>8S。     

Cs(6P)激发态的辐射及与N2碰撞的能量转移

应用激光吸收和荧光方法,测量了Cs(6P)态与N2碰撞的精细结构转移和碰撞猝灭截面。Cs原子被激光激发到6P3/2态,将与泵浦激光束反向平行的检测激光束调到6PJ→8S1/2的跃迁,测量了6PJ激发态的密度及空间分布,由此计算了6PJ→6S的有效辐射率。在T=337 K(蒸气压公式给出Cs密度N0=1.25×1012cm-3)和N2密度2×1016相似文献   

激发态Cs(5D)原子间碰撞能量转移

用激光二步激发Cs原子至8S态,从谱线的波长及强度可以确定Cs原子的辐射及碰撞过程,5D态主要是由8S→7P→5D跃迁布居的.在1016-1017Cs密度范围内,测量了碰撞能量合并5D 5D→nL 6S(nL=9D,11S,7F)速率系数,因5D→6P(3.0-3.6μm)处于红外本实验不能探测,利用一个已经测量过的过程(即6P 5D→6S 7D)作相对测量,对于9D,11S和7F态,其平均速率系数分别为(8.4±4.2)×10-10,(7.3±3.6)×10-10和(9.7±4.8)×10-10cm3s-1.讨论了碰撞转移过程11S 6S 7F 6S对速率系数的影响.     

Preferential excitation transfer in Cs1(6D32)- Cs(6S12) collisions

A cw dye laser beam, tuned near the Cs 8761 Å resonance (Cs¹(6P_{$\text{1}\text{2}$}) → Cs¹(6D_{$\text{3}\text{2}$}) transition) is focused into a Cs vapor. At a Cs density higher than 5 × 10¹⁵ cm^-3, we observe a greater 6P_{$\text{1}\text{2}$} population when the laser is on resonance than when it is off resonance. However, at a lower Cs density, the reverse is observed. This phenomenon is explained as due to the preferential excitation transfer process: Cs¹(6D_{$\text{3}\text{2}$}) + Cs(6S_{$\text{1}\text{2}$}) → Cs¹(6P) + Cs¹(6P), and the corresponding cross secti on is estimated to be (1.5^+1.5_-0.7) × 10^-14 cm² by fitting the experimental results to an approximate rate-equation analysis.     

Energy-pooling collisions in Rb-Cs vapor mixture Rb(5PJ)+Cs(6P3/2) → Rb(5S1/2)+Cs(nlJ'')

Rate coefficients for energy-pooling (EP) collisions Rb(5PJ) + Cs(6P3/2) → Rb(5S1/2) + Cs(nlJ') have been measured.Atoms were excited to Rb(5PJ) and Cs(6P3/2) states using two single-mode diode lasers.To isolate the heteronuclear contribution in the fluorescence spectrum,a double-modulation technique has been adopted.The excited-atom density and spatial distribution are mapped by monitoring the absorption of a counterpropagating single-mode diode laser beam,tuned to Rb(5PJ → 7S1/2) and Cs(6P3/2 →8S1/2) transitions respectively,which could be translated parallelly to the pump beams.The excited atom densities are combined with the measured fluorescence ratios to determine cross sections for the EP processes.It was found that Rb(5P1/2)+Cs(6P3/2) collisions are more efficient than Rb(5P3/2)+Cs(6P3/2)collisions for populating Cs(4F5/2),while the opposite is true for populating Cs(4F7/2).     

Theoretical study of energy transfer in Rb(7S) + Rb(5S) and Rb(5D) + Rb(5S) collisions

We present results of theoretical studies of the non-resonant excitation transfer in Rb(7S) + Rb(5S) and Rb(5D) + Rb(5S) collisions at thermal collision energies. Rb₂ adiabatic molecular terms correlating with the 5S+7S, 5S+5D and 5P+5P states of separated atoms were calculated for internuclear distances R > 20 a.u. using asymptotic approximation. Mechanisms of collisional population and quenching of the 5D state were treated on the basis of the computed molecular terms, and the respective cross-sections were calculated. Theoretical cross-sections are in good agreement with the experimental values at thermal collision energies ( K). Received 13 November 1998 and Received in final form 22 November 1999     

Near threshold photoionization of excited alkali atoms Ak(np) (Ak = Na, K, Rb, Cs; n = 3-6)

The effect of the polarization of the atomic core by the outer electron on near threshold photoionization of excited alkali atoms Ak(np) (Ak = Na-Cs; n=3-6) is investigated. Partial and total cross-sections for photo-ionization of the np-electron were computed utilizing the configuration interaction technique with Pauli-Fock atomic orbitals (CIPF) and including the long range core polarization potential (CP). To calculate the core polarization potential the variational principle is applied. Comparison with previous theoretical results and with available experimental data is made for the total cross-section , for the electron angular distribution parameter , for the ratio of the reduced electric dipole matrix elements and for the phase shift difference , associated with the d-wave and s-wave continua, respectively. In the comparison, new experimental results for , , and , measured for laser-excited, polarized ³⁹K(4p _3/2) atoms, have been included. Received 21 July 1999 and Received in final form 14 October 1999     

Rb(5P)激发态的辐射及与N2碰撞的能量转移

应用激光吸收和荧光方法,测量了Rb(5P)态与N2碰撞的精细结构混合和碰撞猝灭截面.Rb原子被激光激发到5P3/2态,将与泵浦激光束反向平行的检测激光束调到5PJ→7S1/2的跃迁,测量5PJ激发态的密度及空间分布,由此计算了5PJ→5S的有效辐射率,在T=340K和N2密度0.5×1016＜N＜4×1016cm-3范围内测量了5P1/2→5S1/2(794nm)发射的敏化荧光强度I794,量N/I794与N有抛物线型的关系,表明了5PJ的猝灭是由于与N2分子的碰撞产生的,而不是由与Rb基态原子碰撞产生的.由最小二乘法确定的二次多项式的系数得到5P态与N2碰撞精细结构混合截面σ3/2→1/2=(10.43±3.54)×10-16cm2,猝灭截面σD=(9.8±3.4)×10-16cm2.与在不同的实验条件下得到的结果在误差范围内一致.