Study of the Born-Oppenheimer Approximation for Mass-Scaling of Cold Collision Properties

Asymptotic levels of the A $^1\Sigma_u^+$ state of the two isotopomers $^{39}{\rm K}_2$ and $^{39}{\rm K}^{41}{\rm K}$ up to the dissociation limit are investigated with a Doppler-free high resolution laser-spectroscopic experiment in a molecular beam. The observed level structure can be reproduced correctly only if a mass dependent correction term is introduced for the interaction potential. The applied relative correction in the depth of the potential is $10^{-6}$, which is in the order of magnitude expected for corrections of the Born-Oppenheimer approximation. A similar change in ground state potentials might lead to significant changes of mass-scaled properties describing cold collisions like the s-wave scattering length.Comment: 8 pages, 6 figure

The Impact of a School-wide High School Advanced Placement Program and Culture on Participating Students\u27 High School Achievement and Engagement Outcomes and First Year University Academic Success

Along with a high grade point average and high standardized test scores, access and success in higher education is impacted by the courses on a student\u27s transcript. Advanced Placement (AP) courses have set up a cooperative endeavor between secondary schools and colleges, increasing the likelihood of higher levels of educational attainment and early college success. An AP culture which challenges high school students in taking more advanced placement courses can serve as the greatest impact for them as they are bound for college and academic success. This study examined the relationship of AP courses and student achievement as measured by (1) advanced placement course grades, (2) advanced placement test scores. (3) average weighted Grade Point Averages, (4) college entrance ACT scores and (5) engagement as measured by high school participation in (a) athletics, (b) performing arts, and (c) clubs. The study also measured first year university achievement by (1) end of first year university overall grade point averages (2) end of first year university credit hours earned, and (3) continued enrollment for a second year of university studies. Overall findings indicate that students who took advantage of the AP culture provided by this high school and completed a higher number of AP courses achieved a higher rate of academic success and engagement in high school and also were set for a more academically successful first year of university studies

Fourier-transform spectroscopy of Sr2 and revised ground state potential

Precise potentials for the ground state X1Sigma+g and the minimum region of the excited state 2_1Sigma+u of Sr2 are derived by high resolution Fourier-transform spectroscopy of fluorescence progressions from single frequency laser excitation of Sr2 produced in a heat pipe at 950 Celsius. A change of the rotational assignment by four units compared to an earlier work (G. Gerber, R. M\"oller, and H. Schneider, J. Chem. Phys. 81, 1538 (1984)) is needed for a consistent description leading to a significant shift of the potentials towards longer inter atomic distances. The huge amount of ground state data derived for the three different isotopomers 88Sr2, 86Sr88Sr and 87Sr88Sr (almost 60% of all excisting bound rovibrational ground state levels for the isotopomer 88Sr2) fixes this assignment undoubtedly. The presented ground state potential is derived from the observed transitions for the radial region from 4 to 11 A (9 cm-1 below the asymptote) and is extended to the longe range region by the use of theoretical dispersion coefficients together with already available photoassociation data. New estimations of the scattering lengths for the complete set of isotopic combinations are derived by mass scaling with the derived potential. The data set for the excited state 2_1Sigma+u was sufficient to derive a potential energy curve around the minimum.Comment: 10 pages, 7 figures, some small corrections done especially to the potential description of the excited state (already included in the published journal version

Experimental study of the Ca2 1S+1S asymptote

The filtered laser excitation technique was applied for measuring transition frequencies of the Ca$_2$ B-X system from asymptotic levels of the X$^1\Sigma_{\mathrm g}^{+}$ ground state reaching $v''=38$. That level has an outer classical turning point of about 20~\AA which is only 0.2 \rcm below the molecular $^1$S$+^1$S asymptote. Extensive analysis of the spectroscopic data, involving Monte Carlo simulation, allowed for a purely experimental determination of the long range parameters of the potential energy curve. The possible values of the s-wave scattering length could be limited to be between 250$a_0$ and 1000$a_0$.Comment: 10 pages, 7 figure

Universality of weakly bound dimers and Efimov trimers close to Li-Cs Feshbach resonances

We study the interspecies scattering properties of ultracold Li-Cs mixtures in their two energetically lowest spin channels in the magnetic field range between 800 G and 1000 G. Close to two broad Feshbach resonances we create weakly bound LiCs dimers by radio-frequency association and measure the dependence of the binding energy on the external magnetic field strength. Based on the binding energies and complementary atom loss spectroscopy of three other Li-Cs s-wave Feshbach resonances we construct precise molecular singlet and triplet electronic ground state potentials using a coupled-channels calculation. We extract the Li-Cs interspecies scattering length as a function of the external field and obtain almost a ten-fold improvement in the precision of the values for the pole positions and widths of the s-wave Li-Cs Feshbach resonances as compared to our previous work [Pires \textit{et al.}, Phys. Rev. Lett. \textbf{112}, 250404 (2014)]. We discuss implications on the Efimov scenario and the universal geometric scaling for LiCsCs trimers

Hyperfine Structure in the Rotational Spectrum of GaBr

The hyperfine structure of the rotational transition J = 2 ← 1 in the vicinity of 9.8 GHz was measured. The analysis yielded the following quadrupole coupling constants: e qv Q (79Br)= 105.78(34) + 0.92(38) (υ +1/2) MHz, e qv Q (81Br) = 88.55 (35) + 0.60 (32) (υ +1/2) MHz, e qv Q (69Ga) = − 86.68 (30) + 0.36 (24) (υ +1/2) MHz, e qv Q (71Ga) = − 54.58 (25) MHz. These results are consistent with systematic trends in the group of (III a/VII a) -compounds and remove some discrepencies in the literature. © 1978, Walter de Gruyter. All rights reserved

The electronic system (2)2Σ+(2)^2\Sigma^+ and (1)2Π(1)^2\Pi of LiCa

High resolution Fourier transform spectroscopy and Laser induced fluorescence has been performed on LiCa in the infrared spectral range. We analyze rovibrational transitions of the $(2)^2\Sigma^+$--$X(1)^2\Sigma^+$ system of LiCa and find the $(2)^2\Sigma^+$ state to be perturbed by spin-orbit coupling to the $(1)^2\Pi$ state. We study the coupled system obtaining molecular parameters for the $(2)^2\Sigma^+$ and the $(1)^2\Pi$ state together with effective spin-orbit and spin-rotation coupling constants. The coupled system has also been evaluated by applying a potential function instead of rovibrational molecular parameters for the state $(2)^2\Sigma^+$. An improved analytic potential function of the $X(1)^2\Sigma^+$ state is derived, due to the extension of the observed rotational ladder.Comment: 15 pages, 4 figures 2 supplement file