Absorption (logic)

About: Absorption (logic) is a research topic. Over the lifetime, 5733 publications have been published within this topic receiving 236302 citations.

The Spectrum and Structure of Singlet CH$_2$

Abstract: The red absorption bands of CH$\_2$, previously shown to correspond to a transition between singlet states, have been analysed in detail. In the lower electronic state $\tilde a^1$A$\_1$ the molecule is a strongly asymmetric top with rotational constants A$\_{000}$ = 20$\cdot$14, B$\_{000}$ = 11$\cdot$16 and C$\_{000}$ = 7$\cdot$06 cm$^{-1}$. From these constants a CH distance of 1$\cdot$11 $\overset{\circ}{\mathrm A}$ and an HCH angle of 102$\cdot$4$^\circ$ is obtained. In the upper state b$^1$B$\_1$ the molecule is nearly linear, having an HCH angle of about 140$^\circ$ and a CH distance of 1$\cdot$05 $\overset{\circ}{mathrm A}$. Most of the observed absorption bands correspond to excitation of the bending vibration $ u'\_2$ in the upper state (v'$\_2$ = 6, 8, $\ldots$, 18). In some of them in addition the symmetric stretching vibration $ u\_1$ is singly excited. The levels 1, v$\_2$-4, 0 cause strong perturbations in the levels 0, v$\_2$, 0 for v$\_2$ = 8, 10, 12, 14. In the lower state only one excited vibrational level 0, 1, 0 has been established which yields $ u''\_2$ = 1352$\cdot$6 cm$^{-1}$. Fragments of some other singlet absorptions in the near ultraviolet and in the vacuum ultraviolet have been observed and are briefly described. The upper state of the near ultraviolet system is probably the predicted $^1$A$\_1$ state corresponding to $^1\Sigma^+$ in the linear conformation.

Quantum absorption refrigerator.

Abstract: A quantum absorption refrigerator driven by noise is studied with the purpose of determining the limitations of cooling to absolute zero. The model consists of a working medium coupled simultaneously to hot, cold, and noise baths. Explicit expressions for the cooling power are obtained for Gaussian and Poisson white noise. The quantum model is consistent with the first and second laws of thermodynamics. The third law is quantified; the cooling power ${\mathcal{J}}_{c}$ vanishes as ${\mathcal{J}}_{c}\ensuremath{\propto}{T}_{c}^{\ensuremath{\alpha}}$, when ${T}_{c}\ensuremath{\rightarrow}0$, where $\ensuremath{\alpha}=d+1$ for dissipation by emission and absorption of quanta described by a linear coupling to a thermal bosonic field, where $d$ is the dimension of the bath.

Spectroscopy and defect states in polyaniline

Abstract: We report the far-infrared through visible photoinduced absorption (PA) spectra of polyaniline in the emeraldine-base and leucoemeraldine-base forms. The direct-absorption spectrum of emeraldine base (EB) has a broad absorption centered at 2 eV (the ``exciton'' band) and an absorption band at \ensuremath{\sim}3.6 eV (the \ensuremath{\pi}-${\mathrm{\ensuremath{\pi}}}^{\mathrm{*}}$ band gap). The PA spectra of EB for pumping into the ``exciton'' band and across the band gap are nearly identical, indicating the same types of charged defect states are created upon photoexcitation. The direct absorption spectrum of leucoemeraldine base (LB) shows only the \ensuremath{\pi}-${\mathrm{\ensuremath{\pi}}}^{\mathrm{*}}$ band-gap absorption at \ensuremath{\sim}3.6 eV. For pumping into this absorption band, the PA spectrum of LB is very similar to that of EB, although important differences result from the lack of quinoid structures in this material. Based on our results, we propose a model for the photocreation of defect states in leucoemeraldine base and emeraldine base. The central roles of phenyl-ring rotations and of massive polarons are discussed.

Intersubband relaxation in GaAs- Al x Ga 1 − x As quantum well structures observed directly by an infrared bleaching technique

Abstract: Direct intersubband excitations in narrow, modulation doped GaAs-${\mathrm{Al}}_{\mathrm{x}}$${\mathrm{Ga}}_{1\mathrm{\ensuremath{-}}\mathrm{x}}$As quantum well structures are studied by picosecond infrared spectroscopy. The bleaching of the intersubband absorption induced by a high-intensity picosecond pump pulse, is studied by a delayed probe pulse. Typical intersubband relaxation times are of the order of 10 ps at 300 K for a subband splitting of about 150 meV. Polar LO-phonon scattering is discussed as the most relevant relaxation mechanism.

On the Gyromagnetic Ratio and Spectroscopic Splitting Factor of Ferromagnetic Substances

Abstract: A discussion is given of the connection between the results of microwave resonance absorption experiments and gyromagnetic ratio experiments on ferromagnetic substances. A review of the experimental data indicates that the microwave experiments usually give $gg2$, while gyromagnetic measurements usually give values of the related quantity ${g}^{\ensuremath{'}}$ which are 2. The analogous situation obtaining in paramagnetic salts is explained by means of a simple example, and the application of the argument to ferromagnetic substances is indicated. The validity of the use of $g$ in the macroscopic equations of motion in the resonance experiment is justified as a consequence of the approximate mutual cancellation of the orbital and lattice angular momenta. A critical discussion is given of other attempts to explain the $g\ensuremath{ e}{g}^{\ensuremath{'}}$ effect.