Showing papers on "Absorption spectroscopy published in 1978"
310 citations
TL;DR: The absorption spectrum of a Schwarzschild black hole is studied in detail in this article, where phase shifts and absorption cross sections are obtained for a wide range of energy and angular momentum.
Abstract: The absorption spectrum of a Schwarzschild black hole is studied in detail. Accurate and useful computational methods based on the analytical resolution of the wave equation are developed. In this way phase shifts and absorption cross sections are obtained for a wide range of energy and angular momentum. Comparison with the explicit results valid for low and high frequencies is made. The total absorption cross section of the black hole is obtained as a function of the energy. It presents behavior characteristic of a diffraction pattern. The constant geometric-optics limit [$(\frac{27}{4})\ensuremath{\pi}r_{s}^{}{}_{}{}^{2}$] is approached in an oscillatory fashion. The physical interpretation of these results is given and a simple model which describes qualitatively the absorption of waves by the black hole is presented. From these absorption parameters, the Hawking emission rates are calculated and their properties discussed.
205 citations
TL;DR: In this article, optical probe measurements of excited Ce3+ ions in Y3Al5O12 show that stimulated emission in the 550-610nm region is not possible at 295 K because of excited state absorption.
Abstract: Broad bandwidth 5d→4f transitions in Ce3+ have been considered for tunable laser action. In this letter, optical probe measurements of excited Ce3+ ions in Y3Al5O12 show that stimulated emission in the 550–610‐nm region is not possible at 295 K because of excited‐state absorption. Transient measurements demonstrate that part of this loss has ≈75‐ns lifetime and is associated with absorption from the lowest 5d level; a longer‐lifetime loss is also observed. The excited‐state‐absorption loss is reduced at lower temperatures.
184 citations
TL;DR: A laser absorption spectrometer is described which employs a wavelength-tunable Pb(1-x) Sn(x) Se diode in conjunction with a multipass White cell and which is capable of measuring SO(2) concentrations in the low ppb range.
Abstract: A laser absorption spectrometer is described which employs a wavelength-tunable Pb(1-x) Sn(x) Se diode in conjunction with a multipass White cell and which is capable of measuring SO(2) concentrations in the low ppb range. We describe in some detail the modulation techniques used in signal detection which enable us to measure absorption coefficients as low as 10(-7) m(-1). In addition, calibration of the instrumentation using small sample cells is described, and the question of interference from unwanted molecular species is discussed. The instrumentation allows the measurement, basically at the same time, of a large number of other atmospheric gases which are of significance in pollution studies. For example, the present diode operates over 1050-1150 cm(-1) and can measure SO(2), O(3), N(2)O, CO(2), H(2)O, NH(3), and PAN. The addition of a second diode to the system will allow most gases of any atmospheric importance to be monitored. In general, these gases have much stronger ir absorption bands than SO(2) and hence can be detected at concentrations much less than 1 ppb.
182 citations
TL;DR: In this paper, the triplet quantum yield oT by laser flash absorption spectroscopy was derived for the case of triplet triplet oT with laser intensity and actionometry of a laser pulse.
Abstract: — In the comparative method of determining the triplet quantum yield oT by laser flash absorption spectroscopy, general equations are established (1) for describing the dependence of oT with laser intensity and (2) for absolute actionometry of a laser pulse. Applications to specific examples are discussed.
160 citations
TL;DR: Updated tables of vibrational energy levels, molecular constants, band origins, and intensities for carbon dioxide in the infrared region of the spectrum are presented.
Abstract: Updated tables of vibrational energy levels, molecular constants, band origins, and intensities for carbon dioxide in the infrared region of the spectrum are presented. These tables are references for the AFGL Atmospheric Absorption Line Parameters Compilation.
141 citations
133 citations
TL;DR: In this paper, the power dependence of the ion current of Na as a function of the wavelength of the tunable cw dye laser (excitation) and of the Ionizing Ar+- or Kr+-laser, conditions under which true spectra are obtained have been clarified.
Abstract: The investigation of electronic and structural parameters of metal molecules as a function of size may be decisive for understanding and control of heterogeneous catalysis with finely divided metals. Metal-atom clusters can be prepared by several methods, most of which yield a molecular mixture only. Expansion of an atomic vapour into vacuum through a supersonic nozzle creates a complex cluster-spectrum which has been investigated by photoionization using a mass-spectrometer as selective detector. Broad band single photoionization (PI.) yields the abundances and ionization thresholds for Nax(x⩽16), Kx(x⩽12) and NaxKy(x+y⩽6). Rough indications about other deactivation channels of excited alkali-molecules are obtained from an analysis of the photoionization efficiency (PIE.) curves. Two-photon PIE. curves with narrow-band (laser) light sources give an accurate photoionization threshold value and detailed information on ionization processes. Two-photon ionization spectra via a real intermediate state reached by laser excitation are equivalent to normal absorption spectra, if the exciteation step is controlled by the true transition probabilities. By investigation of the power dependence of the ion current of Na as a function of the wavelength of the tunable cw dye laser (excitation) and of the ionizing Ar+- or Kr+-laser, conditions under which true spectra are obtained have been clarified, in good agreement with a photon-kinetic model of the processes involved. Vibronic and rovibronic spectra of several transitions in Na2 and K2 have been measured. Similarly a spectrum of Na3 has been determined mass-selectively. The scope of the new method for an absorption spectroscopy in molecular beams is discussed.
132 citations
TL;DR: In this paper, the optical absorption properties of a high temperature molten salt heat transfer fluid were measured from 0.35 to 2.5 μm using both hemispherical transmission and reflection techniques.
132 citations
130 citations
TL;DR: In this article, a tunable pulsed uv laser was used to photolyze formaldehyde with a time resolution of 1 μs and the energy threshold for radical production was confirmed to be at 86±1 kcal/mole.
Abstract: Formaldehyde vapor was photolyzed with a tunable pulsed uv laser. Flash kinetic absorption spectra of the HCO produced were recorded by intracavity dye laser spectroscopy with a time resolution of 1 μs. The energy threshold for radical production was confirmed to be at 86±1 kcal/mole. Photolysis at 294.1 nm produced HCO in its ground vibronic state (∼2/3) and with one quantum of vibrational excitation in either the bending (∼1/3) or CO stretching (10−1–10−2) vibrations. Observation of the CO stretching hot band absorptions allowed that frequency to be determined as 1868.4±1 cm−1. Quantitative, state‐resolved measurements of concentration vs time were made in pure H2CO and in mixtures with O2, NO, or Ar. The vibrational relaxation rate for the bending vibration of HCO in collisions with H2CO was (4.3±1) ×10−12 cm3 molecule−1 s−1. Reaction rates for HCO+NO→HNO+CO and HCO+O2→HO2+CO were measured as (1.4±0.2) ×10−11 and (4.0±0.8) ×10−12 cm3 molecule−1 s−1, respectively. Approximate rates were determined for t...
TL;DR: In this paper, the electronic absorption spectra of the cation radicals are compared with the photo-electron spectra for the parent molecules in order to find correlations between the two spectra.
Abstract: Cation radicals of some aromatic hydrocarbons, aliphatic amines, and aromatic amines are produced by ..gamma.. irradiation of frozen glassy solutions using organic halides as the solvent. The electronic absorption spectra of the cation radicals are compared with the photoelectron spectra of the parent molecules in order to find correlations between the two spectra. Complementary aspects of the two types of spectroscopy are discussed.
01 Jan 1978
TL;DR: Polarized absorption spectra of lunar pyroxenes with a range of iron, calcium, magnesium, titanium and chromium contents were measured on polished, oriented single crystals; spectral data on pure synthetic FeSiO3 were also recorded.
Abstract: Polarized absorption spectra of lunar pyroxenes with a range of iron, calcium, magnesium, titanium and chromium contents were measured on polished, oriented single crystals; spectral data on pure synthetic FeSiO3 were also recorded. The bands at 1 and 2 microns were found to vary significantly in position with composition within the pyroxene quadrilateral; wavelengths increased with increasing calcium and iron. In the visible region, a weak band at 640 nm correlates in intensity with Cr2O3, but not with titanium as had been previously suggested. The 505-nm ferrous iron peak is a sharp doublet in most low-calcium pyroxenes but a singlet in augites. A peak at 475 nm and an intense absorption edge below 700 nm correlated with titanium content.
TL;DR: In this article, the polarized Raman spectra and infrared powder absorption spectra for PbO ·xSiO2 glasses were measured and interpreted in terms of the structure of the glasses.
Abstract: The polarized Raman spectra and infrared powder absorption spectra for PbO ·xSiO2 glasses, with 0.5⩽x⩽2, were measured and interpreted in terms of the structure of the glasses. Comparison of the spectra of the glasses with the spectra of numerous stable and metastable crystalline phases was also made. It was found that the glasses are composed of a number of silicate species. In glasses for whichx is less than 1, the presence of ionic oxygen (oxygen not bonded to silicon) is confidently inferred from the spectra. A new way of deconvoluting the spectra is also reported.
TL;DR: In this article, resistivity and Hall coefficient measurements were made on a large number of samples at 77 and 300 K and in some cases up to 450 K. Good fits to the log RH vs 1/T plots are obtained by using a model that assumes three kinds of electronic levels within the energy gap: donors, shallow acceptors, and acceptors with an ionization energy of 0.30 eV.
Abstract: Large-grained ingots of CdGeAs2 have been grown from near-stoichiometric melts. Resistivity and Hall coefficient (RH) measurements were made on a large number of samples at 77 and 300 K and in some cases up to 450 K. Good fits to the log RH vs 1/T plots are obtained by using a model that assumes three kinds of electronic levels within the energy gap: donors, shallow acceptors, and acceptors with an ionization energy of 0. 30 eV. The deep acceptors are probably native defects, since their concentration varies by nearly four orders of magnitude from ingot to ingot with little change in impurity concentration. Between the intrinsic absorption edge at about 2. 5 Μm and the two-phonon absorption band at 18 Μm, the optical absorption increases with increasing deep acceptor concentration. By using oriented single-crystal samples ∼ 1 cm on a side, conversion efficiencies as high as 27% have been achieved for second-harmonic generation with single-mode pulses from a CO2 TEA laser.
TL;DR: The kinetics of excited electron states and of the production of molecular and fragmented ions of some polyatomic molecules have been investigated with high temporal resolution.
Abstract: Laser spectroscopy and kinetic mass spectrometry of polyatomic isolated molecules have been carried out by using stepwise laser ionization of molecules in a mass spectrometer The optical absorption spectrum of NO(2) has been recorded, for example, by using pulsed dye-laser excitation and H(2) vacuum-ultraviolet laser ionization of molecules The kinetics of excited electron states and of the production of molecular and fragmented ions of some polyatomic molecules have been investigated with high temporal resolution The sensitivity achieved is 10(-10) cm(-1) of the absorption coefficient and 10(9) (10(5)) molecules in the ground (electronically excited) state in the irradiated volume
TL;DR: Reaction centers have been purified from chromatophores of Rhodopseudomonas viridis by treatment with lauryl dimethyl amine oxide followed by hydroxyapatite chromatography and precipitation with ammonium sulfate and showed three major components of apparent molecular weights 31 000, 37 000 and 41 000.
TL;DR: In this paper, the resonance Raman effect was used to investigate the π-backbonding between Mo and L. The properties of the excited states and the influences of basicity and bulkiness of the PR 3 group on the bonding properties of Mo to L CT bands were discussed.
TL;DR: In this paper, the absorption bands of small molecules containing up to six atoms are clearly identified, allowing the remaining bands to be assigned mainly to larger molecules using the matrix isolation technique.
TL;DR: In this article, the absorption cross-sections of hydrogen peroxide vapor and neutral aqueous solutions were measured in the wavelength range from 195 to 350 nm at 296 K. The spectrophotometric procedure was described, and the reported crosssections are compared with values obtained by other researchers.
Abstract: Absorption cross-sections of hydrogen peroxide vapor and of neutral aqueous solutions of hydrogen peroxide were measured in the wavelength range from 195 to 350 nm at 296 K. The spectrophotometric procedure is described, and the reported cross-sections are compared with values obtained by other researchers. Photodissociation coefficients of atmospheric H2O2 were calculated for direct absorption of unscattered solar radiation, and the vertical distributions of these coefficients are shown for various solar zenith angles.
TL;DR: In this article, hydrogen implantations into silicon samples at room temperature and at 190°C are carried out, and infrared studies are performed on these samples before and following annealing.
Abstract: Hydrogen implantations into silicon samples at room temperature and at 190°C are carried out. Infrared studies are performed on these samples before and following annealing. Previously observed divacancy and hydrogen vibrational bands are found as well as higher-order-bands not previously found in proton irradiation. In addition new hydrogen vibrational bands and other bands are observed and discussed.
In Siliziumproben wird Wasserstoff bei Zimmertemperatur und bei 190°C implantiert. An diesen Proben werden Infrarotuntersuchungen vor und nach Ausheilung durchgefuhrt. Es werden sowohl die fruher beobachteten Doppelleerstellen- und Wasserstoffschwingungsbanden als auch Banden hoherer Ordnungen gefunden, die fruher bei Protonenbestrahlung nicht gefunden wurden. Zusatzlich werden neue Wasserstoffschwingungsbanden und andere Banden beobachtet und diskutiert.
TL;DR: In this paper, collision-induced absorption in the translation-rotation band of H2 and H2-He mixtures has been measured from 20 to 900 kaysers at 77.4, 195, and 292 K. To establish the accuracy of the results, various sources of error are investigated.
Abstract: Collision-induced absorption in the translation-rotation band of H2 and H2-He mixtures has been measured from 20 to 900 kaysers at 77.4, 195, and 292 K. To establish the accuracy of the results, various sources of error are investigated. The zeroth and first spectral moments are evaluated from experiment and theory for H2 at the various temperatures. To obtain theoretical moments consistent with the experimental values, the quantum pair-distribution function must be used. The major portion of the experimental moments can be accounted for by quadrupole-induced dipoles in H2 pairs. The remaining portion is attributable to an anisotropic overlap interaction, although its magnitude depends on the value of the molecular parameters required to calculate the quadrupole contribution.
TL;DR: In this article, electron spin resonance and optical absorption spectroscopy were used to study the photodissociation of nitrosyl haemoglobin and hybrid NO-haemoglobin at liquid helium temperature (4.2°K).
TL;DR: In this paper, the A-X absorption spectra of styrene and styrene-β-D 2 have been photographed at high resolution and vibrationally analyzed, and it is shown that the CH 2 -group of the substituent is perpendicular to the plane of the rest of the molecule in the A state.
TL;DR: In this article, the formation of the new spectrum as CO is dosed is accompanied by a simultaneous decrease in the absorption due to surface states (coordinatively unsaturated surface oxide ions).
Abstract: The adsorption of carbon monoxide at room temperature on well-outgassed specimens of MgO, CaO, SrO and BaO gives rise to a strong absorption spectrum between text-decoration:overlineν= 15000 and text-decoration:overlineν= 40000 cm–1. The stronger the outgassing conditions, the more intense is the absorption which can be developed.The spectrum consists of two main envelopes, one comprising absorption at text-decoration:overlineν= 29000–40000 cm–1 and the other, more composite in character, at text-decoration:overlineν= 15000–29000 cm–1. Changes in the CO pressure affect the two spectral regions differently, showing that two different kinds of adsorbed species are involved.The formation of the new spectrum as CO is dosed is accompanied by a simultaneous decrease in the absorption due to surface states (coordinatively unsaturated surface oxide ions). The effect on the oxide absorption is more pronounced with SrO and CaO than with MgO. The bulk states are unaffected, showing that the process is entirely a surface reaction.The results are interpreted as an electron donor process in which CO accepts electrons from surface oxide ions and forms anionic clusters in the adsorbed state. The high-text-decoration:overlineν absorption (ν > 29 000 cm–1) is ascribed to the dimer (CO)2–2, and the low-text-decoration:overlineν absorption to polymeric oxocarbon anions (CO)xn, where n > 2. The latter are considered to include cyclic, resonance-stabilized structures. The reactivity of the oxide towards CO increases with increase in basic character: on the MgO surface there are relatively few sites of sufficient donor potential to react with CO, but on the more strongly basic CaO and SrO the reaction is much more extensive.
TL;DR: Two types of transient absorptions due to excited diatomic molecules have been observed for neon, argon, and krypton irradiated with electron beam pulses in following wavelength regions: 8000 to 8200 A and 9000 to 10 300 A for Neon, 9500 to 10,000 A and 11 400 to 13 000 A for argon as mentioned in this paper.
Abstract: Two types of transient absorptions due to excited diatomic molecules have been observed for neon, argon, and krypton irradiated with electron beam pulses in following wavelength regions: 8000 to 8200 A and 9000 to 10 300 A for neon, 9500 to 10 000 A and 11 400 to 13 000 A for argon, and 9500 to 10 000 A and 11 600 to 14 000 A for krypton The first absorptions located at shorter wavelengths consist of several discrete bands and their lifetimes are longer than those of the second absorptions located at longer wavelengths In addition, the intensities of the second absorptions are much weaker than those of the first absorptions We have failed to observe the second absorption of xenon, which may be located at longer wavelengths than the observation limit The time‐dependent changes of absorption spectra suggest the formation of vibrationally and rotationally excited molecules We attribute the lower state of the first absorption to the lowest triplet state 1u(3Σ+μ) and the upper one to the state 3Πg resulti
TL;DR: Using a pulsed tunable dye laser pumped by a nitrogen laser, the 5s5p 1P10 level in Sr I was selectively populated from the 5 s2 1S0 ground state as discussed by the authors.
Abstract: Using a pulsed tunable dye laser pumped by a nitrogen laser, the 5s5p 1P10 level in Sr I was selectively populated from the 5s2 1S0 ground state. A simultaneously pumped broad-band dye laser provided a background continuum for photographic registration of absorption spectra. Transitions from the 5s5p 1P10 level to 5sns 1S0 levels and 5snd 1D2 levels were observed with principal quantum number up to n = 36 and n = 52, respectively. Substantial population in the lower lying energy levels 5s4d 1D2 and 5s4d 3D1,2,3 was obtained through radiative and collisional processes, making it possible to get simultaneous registrations of long absorption series out of these energy levels. Transitions from the 5s4d 1D2 level to 5snp 1P10 levels and 5snf 1F03 levels were observed up to n = 29 for both series. From the 5s4d 3D1,2,3 energy levels, transitions were obtained to the 5snf 3F02,3,4 series up to n = 28. An ionization energy of 45 932.09 ± 0.15 cm-1 has been determined for series converging to the 5s 2S1/2 level of Sr II.