Comparison of mesospheric sodium profile retrievals from OSIRIS and SCIAMACHY nightglow measurements

Sodium airglow is generated when excited sodium atoms emit electromagnetic radiation while they are relaxing from an excited state into a lower energetic state. This electromagnetic radiation, the two sodium D-lines at 589.0 nm and 589.6 nm, can usually be detected from space or from ground. Sodium nightglow occurs at times when the sun is not present and excitation of sodium atoms is a result of chemical reaction with ozone. The detection of sodium nightglow can be a means to determine the amount of sodium in the earths' mesosphere and lower thermosphere (MLT). In this study, we present time series of monthly mean sodium concentration profiles, by utilizing the large spatial and temporal coverage of satellite sodium D-line nightglow measurements. We use the OSIRIS/Odin mesospheric limb measurements to derive sodium concentration profiles and vertical column densities and compare those to measurements from SCIAMACHY/Envisat and GOMOS/Envisat. Here we show that the Na D-line Limb Emission Rate (LER) and Volume emission rate (VER) profiles calculated from the OSIRIS and SCIAMACHY measurements, although the OSIRIS LER and VER profiles are around 25 % lower, agree very well in shape and overall seasonal variation. The sodium concentration profiles also agree in shape and magnitude, although those do not show the clear semi-annual cycle which is present in the LER and VER profiles. The comparison to the GOMOS sodium vertical column densities (VCD) shows that the OSIRIS VCDs are in the same order of magnitude although again the semi-annual cycle is not as clear. We attribute the differences in the LER, VER and sodium profiles to the differences in spatial coverage between the two satellite measurements, the lower signal-to-noise ratio (SNR) of the SCIAMACHY measurements and differences in local time between the measurements of the two satellites.

A Quantum Optical Approach to the effect of a Laser Mode on the Motion of Atomic Vapor by Varying the Field Coherence Angles

We follow theoretically the motion of the sodium atoms in vapor state under the influence of a laser mode in (1 + 1) D, which is achieved by introducing different optical filters. In the Dirac interaction representation, the equations of motion are represented via the Bloch form together with the Pauli operators to find the elements of the density matrix of the system. The emergence of the principle of coherence in varying the angles of the laser mode permits the evaluation of the average force affecting the atoms' acceleration or deceleration, and hence the corresponding velocities and temperatures are investigated. The atomic vapor is introduced in a region occupied by a heat bath presented by the laser field, such that the state of the atomic vapor is unstable inside the system due to the loss or gain of its kinetic energy to or from the laser field. This instability is studied by finding the eigenvalues of the system's entropy. Resorting to the assumption of Botin, Kazantsev, and Pusep, who issued in the presence of the weak and strong spontaneous emission, a coupling between the mean numbers of photons in terms of time, which allows the evaluation of the rate of entropy production of the system under study. No singularities are found throughout the process of equations solving and other calculations. Resorting to symbolic software, a set of figures illustrating the nonlinear behavior in the dynamics of the problem is present. In this paper, we introduce a theoretical study of the effect of two-counter propagation traveling plane waves on the motion of the sodium atoms in the vapor state by varying the coherence angles to investigate the atomic behavior. Good agreements are found with previous studies.

Origin of n type properties in single wall carbon nanotube films with anionic surfactants investigated by experimental and theoretical analyses

We investigated the origin of n-type thermoelectric properties in single-wall carbon nanotube (SWCNT) films with anionic surfactants via experimental analyses and first-principles calculations. Several types of anionic surfactants were employed to fabricate SWCNT films via drop-casting, followed by heat treatment at various temperatures. In particular, SWCNT films with sodium dodecylbenzene sulfonate (SDBS) surfactant heated to 350 °C exhibited a longer retention period, wherein the n-type Seebeck coefficient lasted for a maximum of 35 days. In x-ray photoelectron spectroscopy, SWCNT films with SDBS surfactant exhibited a larger amount of sodium than oxygen on the SWCNT surface. The electronic band structure and density of states of SWCNTs with oxygen atoms, oxygen molecules, water molecules, sulfur atoms, and sodium atoms were analyzed using first-principles calculations. The calculations showed that sodium atoms and oxygen molecules moved the Fermi level closer to the conduction and valence bands, respectively. The water molecules, oxygen, and sulfur atoms did not affect the Fermi level. Therefore, SWCNT films exhibited n-type thermoelectric properties when the interaction between the sodium atoms and the SWCNTs was larger than that between the oxygen molecules and the SWCNTs.

Origin of N-Type Thermoelectric Properties in Single-Wall Carbon Nanotube Films With Anionic Surfactants Investigated by Experimental Analyses and First-Principles Calculations

We investigated the origin of n-type thermoelectric properties in single-wall carbon nanotube (SWCNT) films with anionic surfactants via experimental analyses and first-principles calculations. Several types of anionic surfactants were employed to fabricate SWCNT films via drop-casting, followed by heat treatment at various temperatures. In particular, SWCNT films with sodium dodecylbenzene sulfonate (SDBS) surfactant heated to 350°C exhibited a longer retention period, wherein the n-type Seebeck coefficient lasted for a maximum of 35 days. In the color mapping of atomic distribution, SWCNT films with SDBS surfactant exhibited a larger amount of sodium than oxygen on the SWCNT surface. The electronic band structure and density of states of SWCNTs with oxygen atoms, oxygen molecules, water molecules, sulfur atoms, and sodium atoms were analyzed using first-principles calculations. The calculations showed that sodium atoms and oxygen molecules moved the Fermi level closer to the conduction and valence bands, respectively. The water molecules, oxygen, and sulfur atoms did not affect the Fermi level. Therefore, SWCNT films exhibited n-type thermoelectric properties when the interaction between the sodium atoms and the SWCNTs was larger than that between the oxygen molecules and the SWCNTs.

Structural and Dynamics Heterogeneity in Sodium Silicate Liquid

Liquid Na2O-4SiO2 has been constructed by molecular dynamics simulation at 1873 K, ambient pressure under periodic boundary conditions. To clarify the local environment of atoms we apply the oxygen simplex (OS) which is characterized by the size, forming oxygen atom types and the number of sodium located inside the OS. The simulation shows that the liquid comprises the Si-O network and sodium atoms are distributed through different type OSs forming by four O atoms. The number of sodium in particular simplex depends on the size and types of OS. There are five types of OS corresponding to values of n=0÷4. Here n is number of bridge oxygens which an OS passed through. We also found that numerous OSs connected to each other form a long channel where hundreds sodium atoms move. The observed distribution of sodium through Si-O network clearly indicates the structural and dynamics heterogeneity in sodium silicate liquid.