Ground-state hyperfine splitting of antihydrogen

ASACUSA collaboration at CERN’s antiproton decelerator (CERN AD) plans to measure the ground-state hyperfine splitting (GS-HFS) of antihydrogen () to test the CPT symmetry to high precision. Our scheme is to produce an (anti-) atomic beam with a novel two-frequency superconducting Paul trap, and to use sextupole magnets and a 1.4-GHz cavity to analyze the HFS resonance frequency.      

钕离子同位素移位和超精细结构光谱

原子光谱中,同位素移位和超精细结构光谱是少数几个能够将原子物理和原子核物理这两个不同的物理分支联系起来的课题之一.利用共线快离子束-激光光谱学方法测量了单电荷态钕离子4f45d6G3/2→(26041)°5/2跃迁(波长577.21 nm)的共振光谱,得到了所有7个稳定同位素(A=142～146,148,150)之间的能量移位和2个奇同位素(A=143,145)的超精细结构光谱.     

The C hyperfine constants of HCS and HSC studied by microwave spectroscopy

The ¹³C hyperfine constants of the H¹³CS and HS¹³C radicals are determined by microwave spectroscopy. For H¹³CS, the 1₀₁-0₀₀ rotational transition is measured at 38.5 GHz with a Fourier transform microwave spectrometer, and two ¹³C hyperfine constants are determined. They are well interpreted in terms of a relatively large HCS bonding angle (132.8°). For HS¹³C, the N=7-6, 9-8, and 10-9 rotational transitions are measured in the 268-384 GHz region by using a source modulation spectrometer combined with a free-space discharge cell, and five ¹³C hyperfine constants including the nuclear spin-rotation constant, C_aa, are determined. From the ¹³C hyperfine constants, the p character of the unpaired electron orbital on the carbon atom is estimated to be 66.5%, supporting a classical resonance picture; .     

The magnetic hyperfine structure in the rotational spectrum of H2CNH

The hyperfine structure in the ground-state rotational spectrum of methanimine was studied in the frequency range of 64-172 GHz by means of the Lamb-dip technique. This allowed to resolve, in some hyperfine components due to the ¹⁴N nucleus, doublets separated by only some tenth of kHz. We explain the splittings as due to magnetic interactions of the three protons with their molecular environment. The analysis of the experimental spectrum has been guided by quantum-chemical calculations of the hyperfine parameters.     

Spectroscopy apparatus for the measurement of the hyperfine structure of antihydrogen

The ASACUSA CUSP collaboration at the Antiproton Decelerator (AD) of CERN is planning to measure the ground-state hyperfine splitting of antihydrogen (H?) using an atomic spectroscopy beamline. We describe here the latest developments on the spectroscopy apparatus developed to be coupled to the H? production setup (CUSP).     

~(141)Pr~ 581.69nm谱线超精细结构光谱研究

利用共线快离子束 激光光谱学方法测量了正一价镨离子波长 5 81.6 9nm谱线的超精细结构光谱 ,得到了超精细相互作用常数 ;与已发表的数据比较 ,在测量误差范围内一致 ,我们的测量精度提高了一个量级     

The Lamb-dip spectrum of phosphine: The nuclear hyperfine structure due to hydrogen and phosphorus

For the first time, the hyperfine structure of the rotational J = 1 ← 0 (K = 0) and J = 2 ← 1 (K = 0, 1) transitions of phosphine has been resolved by using microwave spectroscopy. To this purpose, the Lamb-dip technique has been employed. In addition, the J = 3 ← 2 (K = 0, 1, 2) transition has been recorded at Doppler resolution. The present investigation allowed us to provide accurate values for most of the hyperfine constants as well as ground state rotational parameters.     

Calculation of the hyperfine structure constants in 85Rb and 133Cs

For heavy atoms or ions, such as, Rb and Cs et al., relativistic effect must be considered in the calculation. In this paper, the relativistic many-body perturbation theory is used to solve the Dirac equation. And the zeroth-order hyperfine constants are evaluated with Dirac-Fock wave function. The finite basis sets of dirac equation are constructed by B-splines. With the finite basis sets the core polarization and the correlation diagrams are calculated. The hyperfine structure constants of the 5S1/2 and 6S1/2 states of 85Rb as well as the 6S1/2 and 7S1/2 states of 133Cs are evaluated.     

Microwave spectrum of PHD: hyperfine structure

The rotational spectrum of the monodeuterated PH₂ radical was studied using a source-modulated submillimeter-wave spectrometer. The PHD radical was generated in a free space absorption cell by a dc-glow discharge in a gas mixture of PH₃ and D₂. Six a-type and 20 b-type rotational transitions were observed in the frequency region of 170-670 GHz. Hyperfine structure due to the deuterium nucleus was resolved only in the rotational transitions of 1₁₁-0₀₀ and 1₁₀-1₀₁ and in the low F₂ components of N=2-1 transitions. A total of 219 spectral lines were measured of which 145 were analyzed by least-squares methods. These yielded 34 precise molecular constants including the hyperfine coupling constants of phosphorus, hydrogen, and deuterium. The principal axes and principal values of the magnetic dipole coupling tensors of hydrogen in PH₂ and deuterium in PD₂ were derived from the observed values of PHD, PH₂ and PD₂. The principal axis of the hydrogen magnetic dipole coupling tensor in PH₂ makes an angle of 2.29° with the PH bond and its T_σ and T_⊥ principal values are determined to be 12.93 and −18.39 MHz, respectively.     

The Lamb-dip spectrum of methylcyanide: Precise rotational transition frequencies and improved ground-state rotational parameters

Methylcyanide, CH₃CN, is an important interstellar species, and therefore the accurate knowledge of precise rest frequencies for rotational transitions as well as ground-state rotational and hyperfine constants is needed. In this work the hyperfine structure of the millimeter- and submillimeter-wave spectra of CH₃CN has been further investigated. In addition, accurate THz measurements have been carried out for the first time. Consequently, the present investigation allowed us to provide the most accurate ground state rotational and hyperfine parameters known at the moment for CH₃C¹⁴N. To resolve the hyperfine structure of the rotational transitions observed, the Lamb-dip technique has been exploited. Both frequency-modulated and video-type detections have been employed.     

Internal rotation and hyperfine coupling interaction in deuterated acetaldehyde

Theoretical and experimental investigations of the hyperfine structure of deuterated acetaldehyde (CD₃COH) are presented. The theoretical approach accounts for the large amplitude internal rotation of the CD₃ group. A hyperfine Hamiltonian, depending on the large amplitude torsional angle, is written taking into account quadrupole hyperfine coupling arising from the three deuterium atoms. Effective hyperfine coupling Hamiltonians are derived for A- and E-type rotation-torsion levels. In the former case, a very symmetrical operator arises in which the hyperfine coupling is the same for all three deuterium atoms. In the latter case the operators are less symmetrical. Hyperfine levels are calculated using symmetry adapted hyperfine wavefunctions in order to build total hyperfine-rotation-torsion wavefunctions satisfying the Pauli exclusion principle. The theoretical approach is used to carry out analyses of six hyperfine patterns which were recorded using a pulsed molecular beam Fourier transform microwave spectrometer. The experimental resolution of this apparatus allows us to resolve individual hyperfine components in many cases. The results of the analysis are consistent with deuterium atoms having an effective quadrupole coupling tensor which, except for appropriate rotations, is quite close to that in CH₃D.     

143,145Nd+ 570.38 nm谱线的超精细结构作用常数测量

利用共线快离子束－激光高分辨光谱学方法测量了^143,145Nd^ 570.38nm谱线的超精细结构光谱，并得到了参与跃迁的上、下能级的超精细相互作用常数。     

Born-Oppenheimer breakdown effects and hyperfine structure in the rotational spectra of SbF and SbCl

Pure rotational spectra have been measured for the ground electronic states of SbF and SbCl. The molecules were prepared by laser ablation of Sb metal in the presence of SF₆ or Cl₂, respectively. Their spectra were measured with a cavity pulsed jet Fourier transform microwave spectrometer. Although both molecules have two unpaired electrons, they are subject to Hund’s coupling case (c), and have X₁0⁺ ground states. The spectra have been interpreted with the formalism of ¹Σ⁺ molecules. For both molecules spectra of several isotopomers have been measured in the ground and first excited vibrational states. Large hyperfine splittings attributable to both nuclear quadrupole coupling and nuclear spin-rotation coupling have been observed. A Dunham-type analysis has produced unusually large Born-Oppenheimer breakdown parameters, which are interpreted in terms of the electronic structures of the molecules.     

Single-photon emission via Raman scattering from the levels with partially resolved hyperfine structure

The probability of emission of a single-photon via Raman scattering of laser pulse on the three-level Λ - type atom in microcavity is studied. The duration of the pulse is considered to be short enough, so that the hyperfine structure of the upper level remains totally unresolved, while that of the lower level is totally resolved. The coherent laser pulse is assumed to be in resonance with the transition between one hyperfine-structure component of the lower atomic level and all hyperfine-structure components of the upper level, while the quantized cavity field is assumed to be in resonance with the transition between the other hyperfine-structure component of the lower level and all components of the upper one. The dependence of the photon emission probability on the mutual orientation of polarization vectors of the cavity mode and of the coherent laser pulse is analyzed. Particularly, the case is investigated, when the total electronic angular momentum of the lower atomic level equals 1/2, which is true for the ground states of alkali atoms employed in the experiments on deterministic single-photon emission. It is shown, that in this case the probability of photon emission equals zero for collinear polarizations of the photon and of the laser pulse, and the probability obtains its maximum value, when the angle between their polarizations equals 60°.     

Measurement of the hyperfine structure of antihydrogen in a beam

A measurement of the hyperfine structure of antihydrogen promises one of the best tests of CPT symmetry. We describe an experiment planned at the Antiproton Decelerator of CERN to measure this quantity in a beam of slow antihydrogen atoms.     

Large scale multi-configuration Hartree-Fock calculation of the hyperfine structure of the ground state of vanadium

The hyperfine structure of the ground state of vanadium, ⁵¹VI, is calculated in the nonrelativistic framework of the multi-configuration Hartree-Fock approximation. A configuration state function limiting algorithm is used to make the calculations feasible and to study the influence of core, valence and core-valence correlations in detail. The obtained configuration state function space captures the most important orbital correlations within 2%. Further correlations are included through configuration interaction calculation. The atomic state functions are used to evaluate the magnetic dipole hyperfine factor A and the electric quadrupole factor B. It turns out that the ab initio calculation can not capture the core polarization of the 2s shell. It introduces an error that is higher than the Hartree-Fock approximation. However, the detailed correlations being observed suggest the introduction of a wrong correlation orbital due to the algorithm being used. Neglecting this orbital leads to good agreement with 2% deviation from the experimental values for the A factors.     

Microwave spectrum of isotopic species of urea (NH2)2CO

We report new microwave measurements for the (¹⁵NH₂)₂CO and (¹⁴NH₂) (¹⁵NH₂)CO isotopologues of urea. The spectra were recorded between 5 and 20 GHz with our MWFT spectrometer coupled to a newly built heated nozzle. A new centrifugal distortion analysis was performed for the (¹⁵NH₂)₂CO species including all available data. For the (¹⁴NH₂) (¹⁵NH₂)CO species the hyperfine structure was recorded for the first time.