High-resolution rotational spectroscopy in a cold ion trap: H2D+ and D2H+

The lowest-lying 1(01) <-- 0(00) transition of para-H(2)D(+) and 1(11) <-- 0(00) of ortho-D(2)H(+) has been detected by the enhancement of the D/H isotope exchange reaction in collisions with p-H2 upon rotational excitation. These are the first pure rotational spectra of molecular ions by action spectroscopy. For this purpose, a cryogenic multipole ion trap has been combined with narrow-band tunable radiation sources operating in the 1.25 to 1.53 THz range. The low temperature of the ions allows us to determine the astronomically important transitions with a relative precision of Delta nu/nu=10(-8). While the 1 476 605.708(15) MHz line center frequency for the o-D(2)H(+) transition agrees very well with previous unpublished work, the 1 370 084.880(20) MHz line center frequency for the p-H(2)D(+) transition deviates by 61 MHz. Potential future applications of this new approach to rotational spectroscopy are discussed.     

Muon level crossing resonance of the R3NMu+ ion

Observation of muon level crossing resonance with¹⁴N nuclei in frozen triethylamine is reported and assigned to the ionic species (C₂H₅)₃NMu⁺. In forming this species, the implanted positive muons mimic the chemical behaviour of protons as usual, here in a process analogous to the protonation of a base. The resultant molecular ion has the axial symmetry necessary for detection of level crossing with an integral-spin nucleus. The quadrupole coupling constant is determined to be ¦e ² qQ/h¦=0.41(4) MHz, corresponding to an electric field gradient on¹⁴N of 0.10(1) a.u. and consistent with anab initio estimate for species of the type R₃NMu⁺. The prospects for detection of the muonium-substituted ammonium ion NH₃Mu⁺ ion in ammonia are discussed.     

Spin lattice coupling coefficients of Co2+ ion in cubic ZnS Crystal

Summary From a uniform and simple method suitable to alld ⁿ ions for the calculation of the spin-lattice coupling coefficientsG ₁₁ andG ₄₄ inT _d symmetry, the analytic expressions ofG ₁₁ andG ₄₄ ford ⁷ ions in this symmetry have been obtained from the high-order perturbation formulae of zero-field splitting in low symmetries based on the weak-field approximation. By using these expressions, the coefficientsG ₁₁ andG ₄₄ for Co²⁺ ion in ZnS crystal have been calculated and the signs of these coefficients are also given. The absolute values of the calculated results show good agreement with the observed values and the signs of these coefficients remain to be verified experimentally. The author of this paper has agreed to not receive the proofs for correction. The project was supported by National Natural Science Foundation of China.     

Static Stark effect in the molecular ion HD+

We present preliminary results on the Stark effect of the hyperfine levels of the molecular ion HD⁺.     

Non-radiative relaxation processes of the Pr3+ ion

Conclusions The³P₀→¹D₂ non-radiative decay rates A_NR of Pr³⁺ and the transition probabilities A_VIB for the vibronic³H₄→³P₀ excitation transitions of Pr³⁺ were measured at 4.2 K in several host lattices. Besides the well-known dependence on the number of phonons involved in the radiationless transition, the multiphonon relaxation rates are observed to be greatly enhanced by increasing covalency and/or decreasing Pr-ligand distances. The enhanced multiphonon relaxation is ascribed to a stronger electron-phonon coupling. The increase in the electron-phonon coupling strength is confirmed by the increase of the vibronic transition probabilities A_VIB in the same sequence as the A_NR rates. The observed host lattice dependence of A_NR can be qualitatively accounted for by a non-linear multiphonon relaxation mechanism. Under certain conditions (viz. low-lying 4f5d states, and a force constant stronger in the 4f5d than in the 4f² states) fast³P₀→¹D₂ non-radiative relaxation via intersystem crossing through the 4f5d state becomes the dominant relaxation mechanism, even at 4.2 K. Debye Institute, Utrecht University P. O. Box 80000, 3508 TA Utrecht, The Netherlands. Published in Zhurnal Prikladnoi Spektroskopii, Vol. 62, No. 4, pp. 63–71, July–August, 1995.     

Ab initio study of rovibronic energies of the CH 2 + molecular ion

The potential energy surfaces of the lowest electronic states $ \tilde X The potential energy surfaces of the lowest electronic states ² A ₁ and ² B ₁ of the CH₂⁺ molecular ion are calculated in the second order of the perturbation theory with the reference function obtained by the multiconfiguration self-consistent-field method in the complete-active-space approximation. Based on the ab initio calculated potential energy surfaces, the rovibronic energies of CH₂⁺ are calculated by the variational method using the RENNER Hamiltonian. It is found that the accuracy of the perturbation theory method involving many reference configurations is as good as the accuracy of the best ab initio calculations performed by the configuration interaction method with many reference configurations and by the coupled cluster method with a single reference configuration. Empirical refinement of the two parameters of the potential function leads to good agreement between calculation and experiment, except for the wavenumbers of the (0, 3, 0)¹ ← (0, 0, 0)⁰ transitions. Original Russian Text ? V.G. Solomonik, A. Yu. Yachmenev, 2008, published in Optika i Spektroskopiya, 2008, Vol. 104, No. 6, pp. 904–910.     

Surface enhancement of molecular ion H_2~+ yield in a 2.45-GHz electron–cyclotron resonance ion source

High current hydrogen molecular ion beam is obtained with a specially designed stainless steel liner permanent magnet2.45-GHz electron–cyclotron resonance(ECR) ion source(PMECR II) at Peking University(PKU). To further understand the physics of the hydrogen generation process inside a plasma chamber, theoretical and experimental investigations on the liner material of the plasma chamber in different running conditions are carried out. Several kinds of materials, stainless steel(SS), tantalum(Ta), quartz, and aluminum(Al) are selected in our study. Experimental results show that stainless steel and tantalum are much better than others in H~+_2 generation. During the experiment, an increasing trend in H~+_2 fraction is observed with stainless steel liner after O_2 discharge inside the ion source. Surface analyses show that the roughness change on the surface after O_2 discharge may be responsible for this phenomenon. After these studies, the pure current of H~+_2 ions can reach 42.3 mA with a fraction of 52.9%. More details are presented in this paper.     

Progress in stored ion beam experiments on atomic and molecular processes

Stored fast ion beams in atomic and molecular collision experiments are discussed with an emphasis on electron–ion interactions at low relative energies. Recent progress was obtained in electron collision spectroscopy using an electron-cooled stored ion beam and a separate electron target in the same storage ring; from a cryogenic photocathode, electron beams with internal temperatures of 5 to 10 K were produced. Results are presented for dielectronic recombination resonances, resolving the hyperfine structure of stored lithiumlike scandium ions and obtaining precise results for the fine structure splitting of these ions, and for ro-vibrational resonances in the recombination of electrons with hydrogen molecular ions, revealing sharp structures down to 2 meV. An overview of the cryogenic storage ring (CSR) project in Heidelberg is given.     

Effect of curve crossing on absorption and resonance Raman spectra: analytical treatment for delta-function coupling in parabolic potentials

We propose an exactly solvable model for the two-state curve-crossing problem. Our model assumes the coupling to be a delta function. It is used to calculate the effect of curve crossing on the electronic absorption spectrum and the resonance Raman excitation profile.     

Einstein A-coefficients for rotational transitions in the HN2O+

EinsteinA-values for the electric dipole transitions between the rotational levels up to 540 cm⁻¹ andJ=11 in the ground vibrational state of the protonated N₂O (i.e., HN₂O⁺) are calculated. The coefficients are used to compute the mean radiative lifetimes of the levels. TheseA-values can be used for analysing the spectra from astronomical objects, if observed.     

Fast Na+ ion conductivity in glass,intermediate and crystalline phases of Na4UO2(SO4)3

The ac electrical conductivity, DSC calorimetry and density data for pure Na₄UO₂(SO₄)₃ and for compound incorporating guest ions Rb⁺, Cd²⁺, Gd³⁺, SiO ₄ ^4– in the glass, quasi-crystalline intermediate and crystalline phases are reported. The glass phase conductivity data show an increase in Na⁺ conductivity by a factor 10³ relative to pure crystalline Na₂SO₄ in the low temperature (LT) region, i.e. 180°C. There is no onset of phase transition up to 260°C. The distinct conductivity regimes prior to devitrification in the glass suggest that higher energy or excited structural states/configurations can exist in the glass phase. The apparent activation energy Q _c value 76±5 kJ/mole for the glass state of all compositions is in excellent agreement with the Na₂SO₄ III Q _c value. The conductivity regime immediately after devitrification with Q _c of 40±3 kJ/mole represents the stable intermediate phase. The conductivity of the final product of devitrification on cooling resembles crystalline behavior except for (Na_3.5Rb_0.5)UO₂(SO₄)₃. A gradual jump in conductivity accompanies the transition in the crystalline sample. The Q _c value is 75±5 kJ/mole for the (HT) phase conductivity in the heating mode but remains constant at 66±5 kJ/mole for the (LT) phase in the heating mode and for both and phases in the cooling mode.The excellent conductivity-volume, i.e. /V correlation is consistent with the free volume contribution to conductivity enhancement and the percolation-type mechanism of transport.This study received partial support from the Natural Sciences and Engineering Research Council of Canada     

He和D2分子相互作用转动激发研究

用T.T(K.T.TangandJ.Peter.Toennies)势模型和公认精密度较高的密耦(Close-Coupling)近似方法计算了E=0.1eV和E=0.2eV时,00-00弹性碰撞及00-02、00-04、00-06非弹性碰撞,得出D2分子转动激发分波截面,并得到了原子与分子碰撞弹性分波截面和非弹性激发截面随量子数增加的变化规律.     

Failure of the molecular core-particle coupling model in C+C inelastic scattering

The single and mutual inelastic excitation of the predominantly single particle p_1/2 →s_1/2 transition in ¹³C has been studied at energies of 8–25 MeV in the center-of-mass system. The results are in striking disagreement with theoretical predictions made using the molecular particle-core coupling model. It is suggested that intermediate states involving different partitions of the valence nucleons among the cores play an important role in these reactions.     

利用快分子离子与固体的相互作用对H2+,HD+和D+2结构的研究

利用快分子离子与固体的相互作用,依靠一套高分辨装置,测量了H2+,HD+和D2+的结构,得到其核间距分别为1.19±0.003 nm、1.25±0.003 nm和1.32±0.003 nm.通过对比,证实了分子离子结构中同位素效应的存在,分析了实验值和理论值存在差别的原因,讨论了实验结果中同位素效应产生的缘由.     

Nuclear quadrupole coupling interactions in the rotational spectrum of tryptamine

Four conformers of tryptamine have been detected in a supersonic expansion and characterized by laser ablation molecular beam Fourier transform microwave spectroscopy LA-MB-FTMW in the 5–10 GHz frequency range. The quadrupole hyperfine structure originated by two ¹⁴N nuclei has been completely resolved for all conformers and used for their unambiguous identification. Nuclear quadrupole coupling constants of the nitrogen atom of the side chain have been used to determine the orientation of the amino group involved in N–H?π interactions: to the π electronic system of the pyrrole unit in the Gauche-Pyrrole conformers (GPy) or to the phenyl unit in the Gauche-Phenyl ones.