High resolution laser spectroscopy of Ba Rydberg atoms

The purpose of the present paper is to illustrate some selected aspects of high resolution laser spectroscopy of Rydberg atoms, rather than giving an extensive review of the state of the art. The following topics will be discussed: (i) Excitation and detection of Ba Rydberg atoms with principal quantum numbers up ton≲300; (ii) Stark effect and atomic diamagnetism of high-n Ba Rydberg states in thel-mixing region, (iii) Resonance in singlet-triplet mixing of 6snp¹P₁ and 6snd¹D₂ Ba Rydberg states deduced from hyperfine structure measurements.     

Study on antiprotonic atoms of light nuclei and isotopes

New data on strong interaction effects in light antiprotonic atoms (N, ¹⁶O, ¹⁸O, S) are presented. For the first time an isotope effect could be observed in p?-¹⁶O/¹⁸O which is used to gain new information about the p?-n interaction in nuclei. A comparison between all existing p?-atomic data and an optical model calculation is performed, yielding a set of fit parameters for the potential.     

Energy levels of light antiprotonic atoms withl>0

The fine and hyperfine structure of light antiprotonic atoms in states of angular momentuml>0 is calculated. The fine (=l-dependent) structure is dominated by vacuum polarization up to a certainl-value (l=4 for¯pp), and by relativistic effects for largerl. Meson exchange is important only in the hyperfine (=spindependent) structure of theP-states. For¯pp and¯p ³He, the hadronic part of the hyperfine structure is dominated byπ ⁰-exchange.     

High resolution resonant Auger spectroscopy of free atoms and molecules

Recent progress in high resolution resonant Auger spectroscopy in the VUV/soft X-ray region is discussed in some detail both from the experimental and theoretical points of view. Some illustrative examples are presented in order to show the progress in the field, emphasized by recent high resolution measurements at “the Finnish beamline”, bl 51, at the MAX I synchrotron radiation facility.     

Measurement of the 4f strong interaction level width in light antiprotonic atoms

The yields of the atomic 4→3 transitions in antiprotonic¹⁴N,^16,17,18O,¹⁹F, and²³Na were measured at the CERN antiproton facility, LEAR. From these, the widths Γ_up of the 4f levels were determined to be 136±19meV (¹⁴N); 603±22 meV (¹⁶O); 731±35 meV (¹⁷O); 795±23 meV (¹⁸O); 2.79±0.16 eV (¹⁹F); and 23.8±7.4 eV (²³Na).     

Strong interaction effects in antiprotonic atoms

Yields of the last observable X-ray transitions in antiprotonic atoms have been measured for groups of neighbouring elements. In sulphur a natural line width and an energy shift could be observed. These data are compared with calculations describing the p?-nucleus interaction in terms of an optical potential using the free p?-N scattering lengths.     

Hadronic lamb shift in antiprotonic atoms

We estimate the difference between the anomalous magnetic moments of bound and free antiprotons and discuss its relevance in the magnetic fine structure of antiprotonic atoms.     

Development of precise nanosecond and picosecond dye lasers for spectroscopy of antiprotonic atoms

Two laser systems were developed by the ASACUSA collaboration of CERN to carry out spectroscopy experiments on antiprotonic atoms. One of these was a continuous-wave pulse-amplified dye laser which was frequency-stabilized to a femtosecond frequency comb. The other generated 700-ps-long laser pulses of wavelengths λ?=?266 and 532 nm using two stimulated Brillouin scattering cells filled with water.     

Nuclear periphery studied with antiprotonic atoms

Two experimental methods were employed to study the nuclear peripheral density. The first method was based on antiprotonic X ray measurements. The widths and shifts of the last atomic state levels available for the antiproton were deduced from the shape of the X-ray lines. These observables are sensitive to the nuclear matter density at a distance 1.5 fm larger than the charge half-density radius. The other method consisted in studying the antiproton annihilation products and gave information on the neutron-to-proton density ratio at a radius 2.5 fm larger than the charge half-density radius. This article presents the results obtained by the PS209 collaboration in measurements performed with the LEAR facility at CERN. Neutron densities and differences of neutron and proton root-mean-square radii were deduced for isotopes over a wide mass range (A = 40–238).     

高谱分辨X光能谱诊断技术

采用国内首次研制出的2 000线/mm的自支撑透射光栅配上背照射软X光CCD(charge coupled device)组成了高谱分辨透射光栅谱仪。通过实验标定和理论模型计算相结合得到了高线对透射光栅的绝对衍射效率;同时建立了透射光栅谱仪测谱解谱方法,编制了相应的解谱程序。在“神光”激光装置上利用该谱仪通过激光打靶实验获得了金腔靶注入口发射的X光能谱定量实验结果,实验结果表明,该谱仪测谱范围在高能区达到6 000eV,谱分辨达到0.1nm,能够清晰地分辨金等离子体M带三峰分布X光谱结构。     

High-power Ti:sapphire lasers for spectroscopy of antiprotonic atoms and radioactive ions

The ASACUSA collaboration has developed injection-seeded Ti:sapphire lasers of linewidth Γ_pl ～ 6 MHz, pulse energy 50–100 mJ, and output wavelength λ?=?726–941?nm. They are being used in two-photon spectroscopy experiments of antiprotonic helium atoms at the Antiproton Decelerator (AD) of CERN. Ti:sapphire lasers of larger linewidth Γ_pl ～ 100 MHz but more robust design will also be used in collinear resonance ionization spectroscopy (CRIS) experiments of neutron-deficient francium ions at the ISOLDE facility.     

Metastable states of antiprotonic helium atoms

We discuss the latest theoretical achievements in calculations of energy transitions in the antiprotonic helium He⁺ p-0304; atoms. New variational calculations of the nonrelativistic energies with precision of ∼10^-10 a.u. and relativistic and QED corrections to the energy levels of mα ⁵ order are presented. This revised version was published online in August 2006 with corrections to the Cover Date.     

X-ray spectroscopy of light hadronic atoms

A series of measurements on light exotic atoms has been performed over the last 15 years at the pion factory of the Paul Scherrer Institut and at CERN’s antiproton facility LEAR using the cyclotron trap and a focusing Bragg crystal spectrometer. The experiments with pions reached already an accuracy close to the presently achievable technical limits. The information on antiprotons remains unsatisfactory because the studies were terminated with the shut down of LEAR. Some aspects of high resolution X-ray spectroscopy are discussed as well as relations between the elementary processes of absorption and annihilation to observables in light nuclei.     

Two-photon spectroscopy of antiprotonic helium

The precision of laser spectroscopy of antiprotonic helium (a helium atom with one of its electrons replaced by an antiproton) has improved by almost 4 orders of magnitude over its 20 years of history. Experimental transition frequencies can be compared to 3-body QED calculations to derive the antiproton-electron mass ratio. In the latest measurements of the Asacusa experiment at CERN, two-photon transitions of antiprotonic helium were excited using two counter-propagating laser beams. This method reduces the Doppler-broadening caused by the thermal motion of the atoms, and allowed us to measure the transition frequencies with a fractional precision of 2.5–5 parts in 10⁹. From these frequencies, we derived an antiproton-electron mass ratio of 1836.1526736(23). Our precision approaches that of the experimental value of the proton-electron mass ratio, and agrees with the latter within errors. Assuming CPT symmetry (i.e. \(m_{p}=m_{\overline {p}}\) ), we further derived the electron’s atomic mass as m _e = 0.0005485799091(7)u from the more accurately known atomic mass of the proton.     

Neutron density distributions deduced from antiprotonic atoms

The differences between neutron and proton density distributions at large nuclear radii in stable nuclei were determined. Two experimental methods were applied: nuclear spectroscopy analysis of the antiproton annihilation residues one mass unit lighter than the target mass and the measurements of strong-interaction effects on antiprotonic x rays. Assuming the validity of two-parameter Fermi neutron and proton distributions at these large radii, the conclusions are that the two experiments are consistent with each other and that for neutron rich nuclei it is mostly the neutron diffuseness which increases and not the half-density radius. The obtained neutron and proton rms radii differences are in agreement with previous results.     

Precision spectroscopy of antiprotonic helium

We survey recent progress in the theoretical study of vibrational transitions in the antiprotonic helium atom. Along with the latest experiment they allow to achieve a competitive accuracy in determination of the atomic mass of an electron and thus they have been included into the CODATA06 analysis of the fundamental constants. Improved theoretical calculation of the hyperfine structure in $^{4\!}\mbox{He}\bar{p}\/$ atom will be considered as well. We will discuss contributions of order $R_\infty\alpha^4$ to the electron spin-orbit interaction. These corrections are necessary to confirm the latest measurements of the 12.9 MHz intervals of the (n,l)?=?(37,35) state in $^4\mbox{He}^+\bar{p}$ and for precise determination of the antiproton magnetic moment.     

High resolution spectroscopy of and

Extensions in frequency coverage coupled with sensitive spectroscopic techniques have enabled high resolution measurements of pure rotational spectra of deuteromethane and its 13-C substituted counterpart up to J^′=7. The current work reveals a small inconsistency in previously reported frequency measurements of ¹²CH₃D at J^′=5.     

High resolution spectroscopy using photodeflection

Isotope separation by laser deflection of an atomic beam, combined with simultaneous mass spectroscopy, has been used to determine optical frequency shifts and to assign mass numbers to all components of the $\text{Ba 6s}{}^2{}^1\text{S}{}_0\text{?6s6p}{}^1\text{P}{}_1$ 5536 Å resonance. Several components which cannot be resolved optically without the use of enriched samples, were resolved with the technique described. They are ${}^{135}\text{Ba}\text{(F=}\text{5}\text{2}\text{)}$ at 120 MHz, ¹³⁶Ba at 128 MHz and ¹³⁴Ba at 138 MHz.