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Observation of a spin-wave sideband in the optical spectrum of MnF sub 2.
Spin wave sideband in absorption spectrum at low temperatures for transition of manganese ion in antiferromagnetic manganese fluoride
Exciton-magnon effects in the optical spectrum of MnF2
Exciton and magnon absorption, emission spectra, and fluorescence of antiferromagnetic manganese fluoride
Periodic flickering in the optical spectrum of HZ Herculis
Photometric observations of HZ Herculis in the ultraviolet with a time resolution of 5 seconds are discussed. The existence of periodic flickering with a time scale of 115 to 130 seconds is observed. The amplitude modulation is about 3 to 6 percent, larger than that associated with the erratic white flickering. The flickering, either erratic or periodic, occurs, but not always, near orbital phase 0.5, irrespective of the on and off parts of the X-ray cycle.
Three-dimensional acousto-optic spectrum analysis
A three-dimensional acoustooptic spectrum analyzer with subhertz resolution is demonstrated experimentally. The first and second dimensions are the two spatial dimensions of the output detector array, and the third dimension is time as sampled by the detector array frame rate. A superfine resolution of 0.12 Hz has been achieved.
An Improved Optical Spectrum and New Model Fits of the Likely Brown Dwarf GD 165B
Long thought by some researchers to be an oddity, GD 165B has instead proven to be the first example of a class of very cool objects (the L dwarfs) which, due to dust formation in their photosphere, lack the dominant bands of TiO seen in warmer M dwarfs.
Manufacture of Sparse-Spectrum Optical Microresonators
An alternative design for dielectric optical microresonators and a relatively simple process to fabricate them have been proposed. The proposed microresonators would exploit the same basic physical phenomena as those of microtorus optical resonators and of the microsphere optical resonators described elsewhere. The resonances in such devices are associated with the propagation of electromagnetic waves along circumferential paths in "whispering-gallery" modes. The main advantage afforded by the proposal is that the design and the fabrication process are expected to be amenable to production of multiple microresonators having reproducible spectral parameters -- including, most notably, high values of the resonance quality factor (Q) and reproducible resonance frequencies.
The Hubble Space Telescope's Near-UV and Optical Transmission Spectrum of Earth as an Exoplanet
We observed the 2019 January total lunar eclipse with the Hubble Space Telescope’s STIS spectrograph to obtain the first near-UV (1700–3200 Å) observation of Earth as a transiting exoplanet. The observatories and instruments that will be able to perform transmission spectroscopy of exo-Earths are beginning to be planned, and characterizing the transmission spectrum of Earth is vital to ensuring that key spectral features (e.g., ozone, or O3) are appropriately captured in mission concept studies. O3 is photochemically produced from O2, a product of the dominant metabolism on Earth today, and it will be sought in future observations as critical evidence for life on exoplanets. Ground-based observations of lunar eclipses have provided the Earth’s transmission spectrum at optical and near-IR wavelengths, but the strongest O3 signatures are in the near-UV. We describe the observations and methods used to extract a transmission spectrum from Hubble lunar eclipse spectra, and identify spectral features of O3 and Rayleigh scattering in the 3000–5500 Å region in Earth’s transmission spectrum by comparing to Earth models that include refraction effects in the terrestrial atmosphere during a lunar eclipse. Our near-UV spectra are featureless, a consequence of missing the narrow time span during the eclipse when near-UV sunlight is not completely attenuated through Earth’s atmosphere due to extremely strong O3 absorption and when sunlight is transmitted to the lunar surface at altitudes where it passes through the O3 layer rather than above it.
The Hubble Space Telescope's Near-UV and Optical Transmission Spectrum of Earth as an Exoplanet
We observed the 2019 January total lunar eclipse with the Hubble Space Telescope’s STIS spectrograph to obtain the first near-UV (1700–3200 Å) observation of Earth as a transiting exoplanet. The observatories and instruments that will be able to perform transmission spectroscopy of exo-Earths are beginning to be planned, and characterizing the transmission spectrum of Earth is vital to ensuring that key spectral features (e.g., ozone, or O{sub 3}) are appropriately captured in mission concept studies. O{sub 3} is photochemically produced from O{sub 2}, a product of the dominant metabolism on Earth today, and it will be sought in future observations as critical evidence for life on exoplanets. Ground-based observations of lunar eclipses have provided the Earth’s transmission spectrum at optical and near-IR wavelengths, but the strongest O{sub 3} signatures are in the near-UV. We describe the observations and methods used to extract a transmission spectrum from Hubble lunar eclipse spectra, and identify spectral features of O{sub 3} and Rayleigh scattering in the 3000–5500 Å region in Earth’s transmission spectrum by comparing to Earth models that include refraction effects in the terrestrial atmosphere during a lunar eclipse. Our near-UV spectra are featureless, a consequence of missing the narrow time span during the eclipse when near-UV sunlight is not completely attenuated through Earth’s atmosphere due to extremely strong O{sub 3} absorption and when sunlight is transmitted to the lunar surface at altitudes where it passes through the O{sub 3} layer rather than above it.
Principles of optical data processing for engineers
Text on optical data processing - optical spectrum analysis, optical correlation, photographic film characteristics, and holography
Dependence of the optical continuous spectrum of quasars on their red-shift
Dependence of optical continuous spectrum of quasi-stellar sources on red shift
Analyses of the excited 5f 1 optical spectra of Th 3+ compounds
We look at the electronic structure of Th(Cp") 3 (Cp" = η 5 -C 5 H 3 (SiMe 3 -1,3), a molecule which has a 6d 1 ground configuration and an excited 5f 1 configuration beginning approximately 14,000 cm -1 higher, is reexamined. The ground state of the 6d 1 configuration in a crystal field of D 3h symmetry is shown to be an orbitally quenched 2 A 1' state, best described as a pure 2 D 1/2 state. Electric dipole selection rules from this state to the states for the 5f 1 configuration in a D 3h crystal field result in the 5f 1 truncated optical spectrum observed. The optical spectrum of the square planar Th 3+ compound [Li(THF) 4 ][Th(OAr') 4 ], where (OAr' = OC 6 H 2 tBu 2 -2,6-Me-4), is discussed.
ACCESS and LRG-BEASTS: A Precise New Optical Transmission Spectrum of the Ultrahot Jupiter WASP-103b
We present a new ground-based optical transmission spectrum of the ultrahot Jupiter WASP-103b (T{sub eq}=2484 K). Our transmission spectrum is the result of combining five new transits from the ACCESS survey and two new transits from the LRG-BEASTS survey with a reanalysis of three archival Gemini/GMOS transits and one VLT/FORS2 transit. Our combined 11-transit transmission spectrum covers a wavelength range of 3900–9450 Å with a median uncertainty in the transit depth of 148 parts per million, which is less than one atmospheric scale height of the planet. In our retrieval analysis of WASP-103b’s combined optical and infrared transmission spectrum, we find strong evidence for unocculted bright regions (4.3σ) and weak evidence for H{sub 2}O (1.9σ), HCN (1.7σ), and TiO (2.1σ), which could be responsible for WASP-103b’s observed temperature inversion. Our optical transmission spectrum shows significant structure that is in excellent agreement with the extensively studied ultrahot Jupiter WASP-121b, for which the presence of VO has been inferred. For WASP-103b, we find that VO can only provide a reasonable fit to the data if its abundance is implausibly high and we do not account for stellar activity. Our results highlight the precision that can be achieved by ground-based observations and the impacts that stellar activity from F-type stars can have on the interpretation of exoplanet transmission spectra.
The integrated optic RF spectrum analyzer
The results of measurements made on a fully integrated optic RF spectrum analyzer (IOSA) are reported. The performance of the device acousto-optic bandwidth, single-tone RF resolution, two-tone RF resolution, single-tone dynamic range, two-tone dynamic range, and single-tone RF response are presented. The device parameters that control device performance are analyzed. These results demonstrate the viability of the IOSA for real time spectrum analysis of pulsed and CW RF signals. Improvements of RF bandwidth resolution can be obtained by the use of larger collimated optical beams which requires larger optical lens elements, and hence, larger crystals.
Further observations of new sources in the AFCRL survey
Salient aspects of follow-up observations carried out on new sources discovered earlier in the AFCRL rocket IR sky survey are summarized. Ground-based searches, studies of class properties of the new AFCRL sources (galactic distribution, IR spectra, time variation), and closer examination of some 'unusual objects' are discussed. Brief descriptions are offered of some unusual objects: possible protostars, and specifically CRL 877; H2O masers in the Mon R2 cloud; the Egg Nebula (CRL 2688); CRL 618, with featureless IR spectrum and optical spectrum reminiscent of a planetary nebula; CRL 437 and other objects associated with multiple-reflection nebulae.
Simultaneous observations of the BL Lacertae object I Zw 187
Two sets of simultaneous spectra consisting of data obtained with radio, IR, optical, UV and X-ray telescopes were obtained 10 months apart for the X-ray bright BL Lac object IZw 187. In addition, nonsimultaneous observations were made in several of the aforementioned observing bands in order to detect flux variations and galactic light contamination was removed from all observations. The BL Lac component is found to have a weak 3000 A bump superposed on an IR-optical-UV spectrum of slope 0.9. Consistent with the arising of the IR-through-X-ray continuum from a single synchrotron source, the X-ray data fall on or near an extrapolation of this power law. No flux variations have been detected in the flat radio spectrum. Optical and X-ray fluxes are observed to vary by a factor not greater than three, and the shortest variability time scales in these bands are comparable at about one week.
Time and space integrating acousto-optic folded spectrum processing for SETI
Time and space integrating folded spectrum techniques utilizing acousto-optic devices (AOD) as 1-D input transducers are investigated for a potential application as wideband, high resolution, large processing gain spectrum analyzers in the search for extra-terrestrial intelligence (SETI) program. The space integrating Fourier transform performed by a lens channels the coarse spectral components diffracted from an AOD onto an array of time integrating narrowband fine resolution spectrum analyzers. The pulsing action of a laser diode samples the interferometrically detected output, aliasing the fine resolution components to baseband, as required for the subsequent charge coupled devices (CCD) processing. The raster scan mechanism incorporated into the readout of the CCD detector array is used to unfold the 2-D transform, reproducing the desired high resolution Fourier transform of the input signal.
Magnetic dipole optical absorption spectrum of MnF sub 2.
Quantitative intensity measurements of magnetic dipole optical absorption transitions in manganese difluoride, discussing Mn ion excited states and magnetic field effects on spectrum