Laser-catalyzed production of ultracold molecules: the 6Li+6Li7Li-->homega6Li-6Li+7Li reaction

We show that by using laser catalysis, we can employ translationally cold (Tr approximately 1.75 K) collisions to produce ultracold (0.01 mKhomega(6Li6Li7Li)*(1(4)A')-->homega6Li6Li+7Li reaction in the collinear approximation. Ultracold 6Li6Li product molecules are shown to be produced at an extraordinary yield of up to 99.97%, using moderate laser intensities of I=100 kW/cm(2)-10 MW/cm2.     

6Li break-up effect on elastic and inelastic scattering of6Li +6Li at 156 MeV

The elastic and inelastic scattering of 156 MeV⁶Li projectiles from⁶Li is studied experimentally and theoretically. The experimental differential cross sections are analyzed by the method of coupled discretized continuum channels in which resonant and non-resonant break-up states of⁶Li are taken into account explicitly. The measured cross sections are simultaneously reproduced quite well by the calculations. Coupling effects of the break-up states are found to play an important role for the scattering.     

Hyperfine interactions in Li2ZrF6 and Li2HfF6

The quadrupole hyperfine interaction in Li₂ZrF₆ and Li₂HfF₆ has been studied as a function of temperature. Both lattices are characterized by very similar low and symmetric electric field gradients at probe sites and no phase transitions were observed up to 770 K. On heating, between 700 and 830 K, the Li₂ZrF₆ undergoes chemical reactions which give rise to ZrO₂ and then to Li₃ZrF₇ (high temperature α-phase) and Li₂ZrO₃. On cooling, below 750 K, the α→β transition in Li₃ ZrF₇ already reported is found to take place. An analogous behaviour is determined for Li₂HfF₆. Accordingly, the same decomposition steps and exstence of high and low temperature phases for Li₃HfF₇ can be inferred.     

The photodisintegration of6Li and7Li

The photodisintegration of the stable Lithium isotopes has been investigated by spectroscopy of the emitted charged particles using the Giessen bremsstrahlung facility. Protons, deuterons, tritons,³He and alpha particles were detected and identified up to 20MeV particle energy. Angular distributions were measured using γ-ray energies up toE _γ =50 MeV. They are compared with theoretical predictions and with other experiments. A remarkable low (γ, t)-cross section was found for both isotopes in disagreement to previous measurements using virtual photons. Coincidence measurements between the emitted particles were performed in order to study the manybody-breakups of⁷Li.     

同位素7Li和6Li的性质殊异

本文研究了同位素7 Li和6 Li在几个方面的性质差异．用相对论量子力学计算指出,6 Li的电子能级比7 Li的能级低,同时,对电偶极E （1）和磁偶极M （1）的能级跃迁波长,6 Li的跃迁波长都要比7 Li的长．由于7 Li和6 Li的核自旋的大小不同,可以看出在磁场2万高斯和温度100－20 K之间,7 Li的磁极化比6 Li的约大13倍．7 Li和6 Li的磁极化这种差异,也是一种可能的同位素7 Li／6 Li的分离方法．     

Single nucleon transfer reactions in6Li+6Li collisions at 156 MeV

Single nucleon transfer reactions in collisions of 156 MeV⁶Li ions with⁶Li nuclei, leading to unstable final nuclei (⁵Li,⁵He) have been experimentally studied. The measured⁶Li(⁶Li,⁷Li)⁵Li_gr and⁶Li(⁶Li,⁷Be)⁵He_gr differential cross sections have been analysed on the basis of a FR-DWBA procedure, looking to which extent the entrance channel optical potentials may account for the unknown exit channel potentials.     

Multibody final states of the 6Li + 6Li reaction AT 97 MeV

Absolute coincidence cross sections were measured for the reactions ⁶Li + ⁶Li → 3α, ⁶Li(⁶Li, 2α), and ⁶Li (⁶Li, 2d), where the latter two represent $\text{N-}\text{body}\text{(N ≧ 4)}$ final states. Broad peaks from the ⁶Li (⁶Li, 2α) reaction are well described by a double spectator pole (DSP) model utilizing a Hulthén wave function, whereas near 40 MeV the DSP peaks are much narrower than predicted. A broad peak in the 3α final-state spectrum, attributed to a single-spectator pole (SSP) process, is well described with the same wave function. The SSP is the principal mechanism for the 3α reaction, in contrast to data near 40 MeV which show that sequential decay from ⁸Be levels is dominant.     

Phase transition in the ternary fluorides Li3Alf6 and Li3CrF6

The phase transitions of two ternary fluorides have been reinvestigated by thermal and X-ray diffraction analyses. Four phase transitions have been detected at T ₁ = 483 ± 5 K, T ₂ = 548 ± 5 K, T ₃ = 765 ± 5 K and T ₄ = 867 ± 5 K for Li₃AlF₆. Only two transformations occurred at T ₁ = 550 ± 5 K and T ₂ = 660 ± 10 K for Li₃CrF₆. Dielectric and optical measurements performed respectively on ceramics and single crystals revealed a ferroelectric behaviour coupling partially with ferroelastic coupling for the two investigated fluorides.     

Excitation function of quasi-free processes in the6Li+6Li → 3α reaction

The⁶Li+⁶Li → 3α reaction was studied at energies around the Coulomb barrier. Excitation functions of the quasi-free processes⁶Li(d,α)⁴ He with an α-particle spectator either in the target or in the beam were measured.     

Buffer-gas-assisted polarization spectroscopy of 6Li

We report on the demonstration of Doppler-free polarization spectroscopy of the D2 line of (6)Li atoms. Counterintuitively, the presence of an Ar buffer gas, in a certain pressure range, causes a drastic enhancement of the polarization rotation signal. The observed dependence of the signal amplitude on the Ar buffer pressure and the pump laser power is reproduced by calculations based on simple rate equations. We performed stable laser frequency locking using a dispersion signal obtained by polarization spectroscopy for laser cooling of (6)Li atoms.     

Charge form factor of Li6

The charge form factor of Li⁶ are calculated using an exponential type of wave function to describe its ground state. The value of the parameter in the wave function is obtained by fitting the root-mean-square radius for the above wave function to the experimental value. We found our calculated charge form factor in excellent agreement with those obtained from electron-Lithium scattering experiments. This shows that our wave function for Li⁶ is quite satisfactory.     

同位素7Li和6Li 的性质殊异和应用

本文研究了同位素7Li和6Li在几个方面的性质差异。用相对论量子力学计算指出,6Li的电子能级7Li的能级低,同时,对电偶极E（1）和磁偶极M(1)的能级跃迁波长,6Li 的跃迁波长都要比7Li 的长。 非相对论量子力学方法（B3LYP/6-311G**）计算总的核自旋-自旋偶合常数 。由于7Li 和6Li 的核自旋大小不同,当其与其它原子偶合时所导致的偶合常数的差异, 是一种可能的分离同位素7Li/6Li 的方法的础。可以看出在磁场2万高斯和温度100-20 K之间 ,7Li的磁极化比6Li的约大13 倍。7Li 和6Li 的磁极化这种差异,也是一种可能的同位素7Li/6Li 的分离方法。     

同位素7Li和6Li 的性质殊异和应用

本文研究了同位素7Li和6Li在几个方面的性质差异。用相对论量子力学计算指出,6Li的电子能级7Li的能级低,同时,对电偶极E（1）和磁偶极M(1)的能级跃迁波长,6Li 的跃迁波长都要比7Li 的长。 非相对论量子力学方法（B3LYP/6-311G**）计算总的核自旋-自旋偶合常数 。由于7Li 和6Li 的核自旋大小不同,当其与其它原子偶合时所导致的偶合常数的差异, 是一种可能的分离同位素7Li/6Li 的方法的础。可以看出在磁场2万高斯和温度100-20 K之间 ,7Li的磁极化比6Li的约大13 倍。7Li 和6Li 的磁极化这种差异,也是一种可能的同位素7Li/6Li 的分离方法。     

Predissociation induced by ungerade-gerade symmetry breaking in 6Li7Li molecule

In the recent sub-Doppler experiment on the B1Pi(u) state of the Li2 molecule by Bouloufa et al. [J. Chem. Phys. 111, 1926 (1999)], where the dissociation of vibrational levels due to the tunneling through the potential barrier was investigated, several vibrational levels with abnormally large dissociated rates were observed in the case of the 6Li7Li isotopomer. This dynamical effect cannot be explained by tunneling as in the case of 6Li2 or 7Li2. A simple model of coupling between B1Pi(u) and 1(1)Pi(g) states involving the u-g symmetry breaking for 6Li7Li is proposed. Rates of the B1Pi(u) predissociated levels due to this coupling are calculated. A good agreement with the experiment is found.     

The reaction 6Li (d, α)α with a new highly polarized 6Li target

A highly polarized ⁶Li target with a new polarizing principe has been developed. A surface is used to store polarized lithium particles from an atomic beam source. The maximum target tensor polarization is P_zz = 0.81 ± 0.06 and the thickness 3 × 10¹⁴ ions per cm².     

Elastic scattering of6Li on6Li in the energy rangeE CM=2–10MeV

In a coincidence experiment, two excitation functions (0_cm=60° and 90°) and four angular distributions of the differential cross section for the elastic scattering of⁶Li on⁶Li were measured. The energy range for the excitation functions was from 2 to 10 MeV (CM), the angular distributions were taken at CM-energies of 4, 5, 6, 7.25 MeV. Optical model calculations were performed. It is shown that the outer portion of the potentials is most important for reproducing the experimental data.     

6Li NMR in lithium borate glasses

In anticipation of using fluctuations in the nuclear dipolar and quadrupolar interaction as a probe of lithium ion motion in lithium borate glasses, the static values of these interactions were measured using a variety of echo techniques. The static quadrupolar echo spectrum of ⁷Li and a calculation of the dipolar interaction in crystalline Li₂B₄O₇ (same chemical composition as the glass under study) were used to estimate the strength of the two interactions. These indicate that the dipolar and quadrupolar interactions for ⁶Li will be of similar size and the dipolar interaction will be dominated by the unlike spin interaction between the ⁶Li and the ¹⁰B, ¹¹B spins. An appropriate theoretical model is proposed and explicit expressions for the echo amplitude are calculated in terms of the dipolar and quadrupolar second moments. This single spin model takes into account the quadrupolar interaction but treats the dipolar interaction as an effective magnetic field. Experimental results are presented which show the essential validity of the model and measurements lead to reasonable values for the dipolar and quadrupolar second moments. The relative merits of the various echo techniques are discussed.