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Collision broadening by molecular hydrogen of sodium and potassium is one of the major broadening mechanisms in the atmospheres of brown dwarf stars and exoplanets at an effective temperature of about 1000K. The accurate computation of line…

Earth and Planetary Astrophysics · Physics 2025-10-08 N. F. Allard , J. F. Kielkopf

Ultracool stellar atmospheres show absorption by alkali resonance lines severely broadened by collisions with neutral perturbers. In the coolest and densest atmospheres, such as those of T dwarfs, Na I and K I broadened by molecular…

Solar and Stellar Astrophysics · Physics 2023-06-21 N. F. Allard , K. Myneni , J. N. Blakely , G. Guillon

We calculate the density shift and broadening of selected dipole transition lines of pionic helium in gaseous helium at low temperatures up to T=12 K and pressure up to a few bar. In the approximation of binary collisions the shift and…

Atomic Physics · Physics 2016-06-15 Boyan Obreshkov , Dimitar Bakalov

We report on our new calculations of unified line profiles of K perturbed by He using ab initio potential data for the conditions prevailing in cool substellar brown dwarfs and hot dense planetary atmospheres with temperatures from…

Solar and Stellar Astrophysics · Physics 2024-03-06 N. F. Allard , J. F. Kielkopf , K. Myneni , J. N. Blakely

We present PHOENIX atmosphere models for metal-rich cool white dwarfs using improved line shapes for the Na I and K I resonance doublets. Profiles for collisional broadening due to H2 and He based on the adiabatic representation show strong…

Rate coefficients for inelastic collisions between Li and H atoms covering all transitions between the asymptotic states Li(2s,2p,3s,3p,3d,4s,4p,4d,4f)+H(1s) and Li^+ +H^- are presented for the temperature range 2000-8000 K based on recent…

Astrophysics · Physics 2009-11-10 P. S. Barklem , A. K. Belyaev , M. Asplund

Quantum mechanical calculations are performed of the emission and absorption profiles of the lithium 2s-2p resonance line under the influence of a helium perturbing gas. We use carefully constructed potential energy surfaces and transition…

Atomic Physics · Physics 2007-05-23 Cheng Zhu , James F. Babb , Alex Dalgarno

Ultracool stellar atmospheres show absorption by alkali resonance lines severely broadened by collisions with neutral perturbers. In the coolest and densest atmospheres, such as those of T dwarfs, Na I and K I broadened by molecular…

Astrophysics · Physics 2009-06-23 Derek Homeier , Nicole F. Allard , France Allard

We study Coulomb drag in a pair of parallel one-dimensional electron systems within the framework of the Tomanaga-Luttinger model. We find that Coulomb coupling has a much stronger effect on one dimensional wires than on two-dimensional…

Mesoscale and Nanoscale Physics · Physics 2009-10-31 Rochus Klesse , Ady Stern

We study electronic transport through a one-dimensional, finite-length quantum wire of correlated electrons (Luttinger liquid) coupled at arbitrary position via tunnel barriers to two semi-infinite, one-dimensional as well as stripe-like…

Strongly Correlated Electrons · Physics 2015-05-13 P. Wächter , V. Meden , K. Schönhammer

Theoretical cross sections for the pressure broadening by hydrogen of rotational transitions of water are compared to the latest available measurements in the temperature range 65-220 K. A high accuracy interaction potential is employed in…

Chemical Physics · Physics 2015-05-19 Laurent Wiesenfeld , Alexandre Faure

We report the low temperature current-voltage (I-V) characteristics studies in quasi-one dimensional conducting polymer nanofibers. We find a threshold voltage Vt below which little current flows at temperatures below 30-40 K. For V > Vt…

Soft Condensed Matter · Physics 2009-11-11 A. N. Aleshin , H. J. Lee , S. H. Jhang , H. S. Kim , K. Akagi , Y. W. Park

Using the semiclassical perturbation method, electron-, proton-, and ionized helium-impact line widths and shifts for the nine Cr I spectral lines from the $4p^7P^0-4d^7D$ multiplet, have been calculated for a perturbers density of…

Astrophysics · Physics 2009-11-10 M. S. Dimitrijevic , T. Ryabchikova , L. C. Popovic , D. Shulyak , S. Khan

We report pressure broadening coefficients for the 21 electric-dipole transitions between the eight lowest rotational levels of ortho-H$_2$O and para-H$_2$O molecules by collisions with He at temperatures from 20 to 120 K. These…

Chemical Physics · Physics 2016-06-07 M. I. Hernández , J. M. Fernández , G. Tejeda , E. Moreno , S. Montero

The dependence on applied electric field ($0 - 40$ kV/cm) of the scintillation light produced by fast electrons and $\alpha$ particles stopped in liquid helium in the temperature range of 0.44 K to 3.12 K is reported. For both types of…

The paper presents a simplified formula to determine an electron temperature, Te(He I), for planetary nebulae (PNe) using the He I 7281/6678 line flux ratio. In our previous studies of Te(He I) (Zhang et al. 2005), we used the He I line…

Astrophysics · Physics 2007-05-23 Y. Zhang , R. H. Rubin , X. -W. Liu

Thermophysical properties of hydrogen, helium, and hydrogen-helium mixtures have been investigated in the warm dense matter regime at electron number densities ranging from $6.02\times10^{29}\sim2.41\times10^{30}$/m$^{3}$ and temperatures…

Materials Science · Physics 2015-06-16 Cong Wang , Xian-Tu He , Ping Zhang

We report our transport studies in quasi one-dimensional (1D) conductors - helical polyacetylene fibers doped with iodine and the data analysis for other polymer single fibers and tubes. We found that at 30 K < T < 300 K the conductance and…

Soft Condensed Matter · Physics 2009-11-10 A. N. Aleshin , H. J. Lee , Y. W. Park , K. Akagi

The specific heat of liquid helium was calculated theoretically in the Landau theory. The results deviate from experimental data in the temperature region of 1.3 - 2.1 K. Many theorists subsequently improved the results of the Landau theory…

Other Condensed Matter · Physics 2009-11-13 Shosuke Sasaki

Recent experiments have revealed that the temperature dependence of the conductance of quasi-ballistic quantum wires bears clear features of the Luttinger-liquid state. In this paper, the conductance of an N-channel quantum wire is…

Mesoscale and Nanoscale Physics · Physics 2009-10-30 Nancy Sandler , Dmitrii L. Maslov
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