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

Observational Results of a Multi-Telescope Campaign in Search of Interstellar Urea [(NH2_2)2_2CO]

In this paper, we present the results of an observational search for gas phase urea [(NH$_2$)$_2$CO] observed towards the Sgr B2(N-LMH) region. We show data covering urea transitions from $\sim$100 GHz to 250 GHz from five different observational facilities: BIMA, CARMA, the NRAO 12 m telescope, the IRAM 30 m telescope, and SEST. The results show that the features ascribed to urea can be reproduced across the entire observed bandwidth and all facilities by best fit column density, temperature, and source size parameters which vary by less than a factor of 2 between observations merely by adjusting for telescope-specific parameters. Interferometric observations show that the emission arising from these transitions is cospatial and compact, consistent with the derived source sizes and emission from a single species. Despite this evidence, the spectral complexity, both of (NH$_2$)$_2$CO and of Sgr B2(N), makes the definitive identification of this molecule challenging. We present observational spectra, laboratory data, and models, and discuss our results in the context of a possible molecular detection of urea.Comment: 38 pages, 9 Figures, accepted in the Astrophysical Journa

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}

Infrared and Millimeter-Wave Study of the Four Lowest Torsional States of CH3CF3

An investigation of the torsion-rotation Hamiltonian of CH3CF3 in the ground vibrational state has been carried out using infrared and mm-wave spectroscopy. With infrared Fourier transform spectroscopy, the weak, torsional overtone (v6 = 2 <-- 0) has been studied leading to the measurement of 382 frequencies between 405 and 440 cm-1 at a resolution of 0.005 cm-1. Torsional splittings on the order of 0.03 cm-1 were observed. With mm-wave methods, a total of 669 rotational transitions between 50 and 360 GHz have been measured at Doppler-limited resolution in the four lowest torsional states v6 = 0, 1, 2, 3. The experimental uncertainty attained for an isolated line was better than 10 kHz below 150 GHz, and somewhat larger at higher frequencies. For v6 = 3, torsional splittings as large as 8.7 MHz were observed. The global data set consisted of the current frequency determinations and the 443 measurements with molecular beam, microwave, and mm-wave methods analyzed by I. Ozier, J. Schroderus, S.-X. Wang, G. A. McRae, M. C. L. Gerry, B. Vogelsanger, and A. Bauder [J. Mol. Spectrosc. 190, 324-340 (1998)]. The observation of mm-wave R-branch transitions for v6 = 1 led to a change in the J-assignment of the forbidden ([Delta]k = ?3) transitions reported earlier for this torsional state. A good fit was obtained by varying 24 parameters in a Hamiltonian that represented both the torsional effects and the sextic splittings. In the earlier work, the large reduced barrier height led to high correlations among several of the torsional distortion constants. With the current measurements, many of these correlations are substantially reduced. Improved effective values were determined for the height V3 of the hindering barrier and the first-order correction V6 in the Fourier expansion of the potential function. The dipole function which characterizes the transition moment of the torsional overtone (v6 = 2 <-- 0) can be written as the product of a single effective dipole constant [mu]T0,eff and the appropriate off-diagonal matrix element of (1 - cos 3[alpha])/2, where [alpha] is the torsional angle. From an intensity analysis of the infrared spectrum, it has been determined that [mu]T0,eff = 85.3(62) mD. A novel approach based on a simple regrouping of angular momentum operators is introduced for decoupling the torsional and rotational degrees of freedom.NRC publication: Ye