Effect of photoions on the line shapes of the F\"orster resonance and microwave transitions in cold rubidium Rydberg atoms

Experiments on the spectroscopy of the F\"orster resonance Rb(37P)+Rb(37P) -> Rb(37S)+Rb(38S) and microwave transitions nP -> n'S, n'D between Rydberg states of cold Rb atoms in a magneto-optical trap have been performed. Under ordinary conditions, all spectra exhibited a 2-3 MHz line width independently of the interaction time of atoms with each other or with microwave radiation, although the ultimate resonance width should be defined by the inverse interaction time. Analysis of the experimental conditions has shown that the main source of the line broadening was the inhomogeneous electric field of cold photoions appeared at the excitation of initial Rydberg nP states by broadband pulsed laser radiation. Using an additional pulse of the electric field, which rapidly removed the photoions after the laser pulse, lead to a substantial narrowing of the microwave and F\"orster resonances. An analysis of various sources of the line broadening in cold Rydberg atoms has been conducted.Comment: 10 pages, 6 figure

Ionization of Rydberg atoms by blackbody radiation

We have studied an ionization of alkali-metal Rydberg atoms by blackbody radiation (BBR). The results of the theoretical calculations of ionization rates of Li, Na, K, Rb and Cs Rydberg atoms are presented. Calculations have been performed for nS, nP and nD states which are commonly used in a variety of experiments, at principal quantum numbers n=8-65 and at the three ambient temperatures of 77, 300 and 600 K. A peculiarity of our calculations is that we take into account the contributions of BBR-induced redistribution of population between Rydberg states prior to photoionization and field ionization by extraction electric field pulses. The obtained results show that these phenomena affect both the magnitude of measured ionization rates and shapes of their dependences on n. A Cooper minimum for BBR-induced transitions between bound Rydberg states of Li has been found. The calculated ionization rates are compared with our earlier measurements of BBR-induced ionization rates of Na nS and nD Rydberg states with n=8-20 at 300 K. A good agreement for all states except nS with n>15 is observed. Useful analytical formulas for quick estimation of BBR ionization rates of Rydberg atoms are presented. Application of BBR-induced ionization signal to measurements of collisional ionization rates is demonstrated.Comment: 36 pages, 16 figures. Paper is revised following NJP referees' comments and suggestion

Peptide composition of extracts of cryopreserved pigs’ and piglets’ heart fragments

It is known that extracts of cryopreserved organ fragments of pigs and piglets stimulate the processes of reparative regeneration. Therefore, the study of the extracts is essential for understanding the mechanism of their biological effects. In this paper was studied the molecular mass distribution of peptides in the extracts of cryopreserved heart fragments of pigs’ and piglets’, i.e., the chromatograms of pigs’ heart extracts show 3 picks, whilst piglets’ heart extract show 6 picks. The peculiarity of pigs’ heart extracts is the absence of peptides with molecular mass of 10,000 and more. The differences in the intensity of extracts fluorescence prove that the peptides in pigs’ heart extracts contain greater amount of tryptophan residues accessible for solvent. The synchronous fluorescence spectra of extracts were obtained which allows the identification of extract without assessment of their components. Results shown in this research could be used for control and standardization of heart extracts peptide composition under investigation of their biological quality

MILLIMETER WAVE SPECTRUM OF ACETAMIDE

$^{a}$The millimeter wave part of the investigation was supported by STCU under contract 2132Author Institution: Institute of Radio Astronomy of NASU; CNRS, Laboratoire de Photophysique Mol\'{e}culaire, Universit\'{e} Paris Sud; Optical Technology Division, National Institute of Standards and TechnologyWe are reporting recent progress in measuring, assigning and fitting the millimeter wave rotational transitions of the ground torsional state (and a few lines of the first excited torsional state) of the acetamide molecule $CH_{3}CONH_{2}$. The new measurements of the acetamide spectrum have been carried out using the microwave spectrometer in Kharkov between 50-150 GHz. We have assigned 331 and 199 new rotational transitions belonging to the A and E species respectively and involving J up to 20 and $K_{a}$ up to 10. The observed spectrum was analyzed using the so-called rho axis method (RAM) which was applied in the past to several internal rotors with success. After having removed the observed hyperfine splittings due to the quadrupole coupling, this new data along with 115 previously published measurements are fitted using 32 parameters of the RAM Hamiltonian with root-mean-square deviations of 37 kHz and 49 kHz for the $630 V_{t}=0$ lines belonging to the ground torsional state and for the $15 v_{t}=1$ lines belonging to the excited torsional state respectively. Separate rms deviations for the A (32 kHz) and for the E (44 kHz) species indicate similar quality of the fit for the two symmetry species. The main difficulty which is encountered now in the assignment process of the higher J and K values of the A species in the first excited torsional state and in even the ground torsional state of the E species is caused by the problem of finding a correct K label for the eigenvectors corresponding to energy levels involved in the fit (so-called labeling problem). We will discuss this problem and other aspects which make the acetamide molecule a rather typical model molecule for future studies on polypeptide mimetics.$^{a}

Ionization of deep impurities by far-infrared radiation

An analysis is made of the ionization of deep impurity centers by high-intensity far-infrared and submillimeter-wavelength radiation, with photon energies tens of times lower than the impurity ionization energy. Within a broad range of intensities and wavelengths, terahertz electric fields of the exciting radiation act as a dc field. Under these conditions, deep-center ionization can be described as multiphonon-assisted tunneling, in which carrier emission is accompanied by defect tunneling in configuration space and electron tunneling in the electric field. The field dependence of the ionization probability permits one to determine the defect tunneling times and the character of the defect adiabatic potentials. The ionization probability deviates from the field dependence e(E)}exp(E2/Ec 2) (where E is the wave field, and Ec is a characteristic field) corresponding to multiphonon-assisted tunneling ionization in relatively low fields, where the defects are ionized through the Poole–Frenkel effect, and in very strong fields, where the ionization is produced by direct tunneling without thermal activation. The effects resulting from the high radiation frequency are considered and it is shown that, at low temperatures, they become dominant