TY - JOUR A1 - Gedzelman, S. D. A1 - Vollmer, Michael T1 - Progress in atmospheric optics and light and color in nature JF - In: Bulletin of the American Meteorological Society : BAMS 90 (2009), 689-693 Y1 - 2009 SN - 0003-0007 SP - 689 ER - TY - JOUR A1 - Vollmer, Michael T1 - Mirrors in the Air: Mirages in Nature and in the Laboratory JF - In: Physics Education 44 (2009) 2, 165-174 Y1 - 2009 SN - 0031-9120 SP - 165 EP - 174 ER - TY - JOUR A1 - Vollmer, Michael A1 - Möllmann, Klaus-Peter T1 - Michelson Interferometer for your kitchen table JF - In: The Physics Teacher 46 (2008), 114-117 Y1 - 2008 SN - 0031-921x SP - 114 EP - 117 ER - TY - JOUR A1 - Planinsic, G. A1 - Vollmer, Michael T1 - The surface to volume ratio in thermal physics: from cheese cube physics to animal metabolism JF - In: European Journal of Physics 29 (2008), 369-384 Y1 - 2008 SN - 0143-0807 SP - 369 EP - 384 ER - TY - JOUR A1 - Vollmer, Michael A1 - Möllmann, Klaus-Peter A1 - Arnold, F. T1 - Locomotion by blowing into the sail of a sailboat? From a basic physics question to thrust reversal of jet airplanes JF - In: Physics Education 42 (2007), 369-377 Y1 - 2007 SN - 0031-9120 SP - 369 EP - 377 ER - TY - JOUR A1 - Vollmer, Michael A1 - Möllmann, Klaus-Peter T1 - Infrared thermal imaging as a tool in university physics education JF - In: European Journal of Physics 28 (2007), S37-S50 Y1 - 2007 UR - http://iopscience.iop.org/0143-0807/28/3/S04/pdf/0143-0807_28_3_S04.pdf SP - 37 EP - 50 ER - TY - JOUR A1 - Möllmann, Klaus-Peter A1 - Vollmer, Michael T1 - Measurements and predictions of the illuminance during a solar eclipse JF - In: European journal of physics 27 (2006), 1299-1314 N2 - Measurements of illuminance during a solar eclipse are presented. The data are compared to theoretical predictions, based on a geometrical model for obscuration. The model assumes a straight and uniform motion of the sun and moon as well as a spherical shape of both, i.e. it neglects any effects of limb darkening. Furthermore, the sun's disk is assumed to have homogeneous luminosity, i.e. any luminosity variations due to sun spots are neglected. Input parameters are the duration of the eclipse, the duration of totality, the impact parameter, i.e. the distance between the two trajectories of sun and moon, and the sizes of sun and moon. The model applies to all types of eclipses, partial, annular and total. Y1 - 2006 SP - 1299 EP - 1314 ER - TY - JOUR A1 - Vollmer, Michael A1 - Gedzelman, S. D. T1 - Colors of the sun and moon : the role of the optical air mass JF - In: European journal of physics 27 (2006), 299-309 N2 - A geometric model for the optical air mass of the atmosphere is developed. Using the model, simple formulae are derived for the optical thickness of light passing through (1) a molecular atmosphere, (2) an atmosphere with uniformly distributed tropospheric aerosols and (3) atmospheres with elevated aerosol layers. The formulae are used to model the spectra and perceived colours of the Sun and Moon. Y1 - 2006 SP - 299 EP - 309 ER - TY - JOUR A1 - Schneider, Werner B. A1 - Vollmer, Michael T1 - Experimental simulations of pollen coronas JF - In: Applied optics 44 (2005) 27, 5746-5753 N2 - A procedure to experimentally simulate pollen coronas is discussed. Observed coronas are due to pine and birch pollen having different geometries. Using computer simulations, two-dimensional projections of a large number of pollenlike objects with adjustable shapes, with or without preferential orientation and statistical or regular spatial distribution, are generated. The photograph of the printout allows samples with typical sizes between 20 and 200 µm. Their diffraction patterns can closely resemble the ones observed in nature and predicted by theory. © 2005 Optical Society of America Y1 - 2005 U6 - https://doi.org/10.1364/AO.44.005746 SP - 5746 EP - 5753 ER - TY - CHAP A1 - Möllmann, Klaus-Peter A1 - Lutz, Norbert A1 - Vollmer, Michael A1 - Wille, Ch. T1 - Thermography of Microsystems T2 - In: InfraMation proceedings Vol. 5 (2004), 183-196 Y1 - 2004 SP - 183 EP - 196 ER - TY - JOUR A1 - Vollmer, Michael A1 - Greenler, Robert T1 - More Halo and Mirage Experiments in Atmospheric Optics JF - In: Applied Optics 42 (2003) 3, pp. 394-398 N2 - Some laboratory demonstrations on atmospheric optics are presented. The focus is on dispersion effects in mirages, lateral mirages, and inferior mirages produced with small hot plates. We also show a demonstration of the upper-tangent-arc halo, produced with a hexagonal prism, rotating about two axes. © 2003 Optical Society of America Y1 - 2003 U6 - https://doi.org/10.1364/AO.42.000394 ER - TY - JOUR A1 - Vollmer, Michael A1 - Tammer, Robert T1 - Laboratory Experiments in Atmospheric Optics JF - In: Applied optics 37 (1998) 9, pp. 1557-1568 N2 - Old and new laboratory experiments on atmospheric optics with a focus on mirages, rainbows, and halos are presented. Some qualitative demonstrations serve primarily didactical purposes, e.g., by proving the existence of curved light rays in media with a gradient of the index of refraction, by directly visualizing the minimum-deviation curve for rainbow paths in water droplets, or by helping to elucidate the ray classes in hexagons that contribute to a specific halo. In addition, quantitative experiments allow a direct comparison of angular positions and intensities with analytical computations or Monte Carlo simulations of light scattering from small water droplets or ice hexagons. In particular, the latter can help us to understand complex halo phenomena. © 1998 Optical Society of America Y1 - 1998 U6 - https://doi.org/10.1364/AO.37.001557 SP - 1557 EP - 1568 ER - TY - JOUR A1 - Götz, T. A1 - Hoheisel, W. A1 - Träger, F. A1 - Vollmer, Michael T1 - Characterization of Large Supported Metal Clusters by Optical Spectroscopy JF - In: Zeitschrift für Physik / D Vol. 33 (1995) 2, pp 133-141 N2 - Small sodium and silver particles were generated on dielectric substrates like LiF, quartz and sapphire under ultrahigh vacuum conditions. The optical transmission spectra of the clusters were measured as a function of cluster size and shape, for low and high substrate temperatures as well as for s- and p- polarization of the incident light. Excitation of dipolar surface plasmon oscillations in the directions normal and parallel to the substrate surface could be identified. Furthermore, optical spectra for Na and Ag clusters were calculated with the classical Mie theory. The measured spectra vary strongly if the experimental conditions are changed and can be exploited, for example, to characterize the particles with regard to their size and shape. In particular, the axial ratio of the spheroidal clusters could be determined. Its value is considerably different for the two investigated metals and depends on the substrate material. Furthermore, the temperature of the substrate has a pronounced influence on the shape of the particles. At low temperature of T=100 K two-dimensional island growth is predominant. The particles extend only little in the direction perpendicular to the surface and coalesce readily at small coverage of metal atoms. In contrast, the clusters are truly three-dimensional at T=300 K. At this stage, sodium particles still exhibit a rather small axial ratio whereas silver clusters appear almost spherical. Thus, measurements of the optical spectra permit direct in situ monitoring of cluster growth during the nucleation of adsorbed atoms and of temperature induced shape variations. In addition to investigations of the shape of the particles, the quadrupolar surface plasmon mode was observed for Ag clusters. Y1 - 1995 U6 - https://doi.org/10.1007/BF01437432 ER - TY - CHAP A1 - Vollmer, Michael T1 - Ablation of Metal Particles with Laser Light: Shape and Polarization Effects T2 - In: Laser ablation: mechanisms and applications - II : second international conference, Knoxville, TN April 1993 / eds.: John C. Miller ...- New York : American Inst. of Physics, 1994. - (AIP conference proceedings / American Institute of Physics. - Melville, NY, 1970- ; 288) (Laser ablation: mechanisms and applications. - New York : American Institute of Physics ; 2). - S. 32 ff Y1 - 1994 SP - 32 EP - 37 ER - TY - JOUR A1 - Hövel, H. A1 - Fritz, S. A1 - Hilger, A. A1 - Kreibig, U. A1 - Vollmer, Michael T1 - Width of cluster plasmon resonances: Bulk dielectric functions and chemical interface damping JF - In: Phys. Rev. B 48 (1993) 24, 18178–18188 N2 - The damping of collective electron resonances in clusters which develop into plasmon polaritons at larger sizes is investigated for free, supported, and embedded neutral metal clusters. Embedding of free 2 nm Ag clusters of 2-nm diameter into a SiO2 matrix leads to an increase of the width of the resonances by more than a factor of 3. The optical spectra are compared with the Mie theory using size-effect-modified dielectric functions of the solid state. The results corroborate the assumption that the widths of the resonances strongly depend on chemical interface effects. The results are briefly discussed with regard to limited-mean-free-path and quantum-size-effect theories and a recent approach by Persson. It is demonstrated that the widths of the spectra of supported and embedded clusters have to be interpreted with care since true intrinsic size effects of the clusters appear to be less effective than previously believed and can be obscured by the chemical interface damping. © 1993 The American Physical Society Y1 - 1993 U6 - https://doi.org/10.1103/PhysRevB.48.18178 ER - TY - JOUR A1 - Götz, T. A1 - Träger, F. A1 - Vollmer, Michael T1 - Desorption of metal atoms with laser light of different polarization JF - In: Applied physics / A 57 (1993) 1, pp 101-104 N2 - Laser-induced desorption of metal atoms from the surface of small metal particles has been investigated as a function of the shape of the particles and the polarization of the incident laser light. The particles were supported on LiF, quartz or sapphire substrates. In a first set of experiments, the shape of the particles was determined by recording optical transmission spectra with s- and p-polarized light incident under an angle of typically 40° with respect to the surface normal. The metal particles turn out to be oblate, the ratio of the axes perpendicular and parallel to the substrate surface being on the order of 0.5. This ratio decreases with increasing particle size. Also, the particles change shape if the temperature is raised. In further experiments, s- and p-polarized light has been used to stimulate desorption of atoms via surface plasmon excitation. It is found that the desorption rate markedly depends on the polarization of the light. This is explained by excitation of the collective electron oscillation along different axes of the non-spherical particles. Y1 - 1993 U6 - https://doi.org/10.1007/BF00331225 SP - 101 EP - 104 ER - TY - JOUR A1 - Hoheisel, W. A1 - Vollmer, Michael A1 - Träger, F. T1 - Desorption of metal atoms with laser light: Mechanistic studies JF - In: Physical Review / B 48 1993) 23, 17463-17476 N2 - Results on laser-induced desorption of metal atoms from small metal particles are presented. Experiments have been performed on sodium, potassium, and silver particles supported on a LiF(100) single-crystal surface under ultrahigh vacuum conditions. Measurements include the determination of the desorption rate as a function of laser wavelength, laser intensity, average particle size, and substrate temperature, the determination of the kinetic energy of the desorbed atoms, the investigation of the optical spectra of the supported metal particles, and the study of the influence of adsorbate molecules on the desorption rate. Furthermore, theoretical extinction and absorption spectra of the metal particles have been calculated with the classical electrodynamical Mie theory as a function of average particle size and excitation wavelength. Also, the radial electric field at the particle surface was computed. The results of the experiments and theoretical calculations are combined to give a consistent picture of the mechanism of metal-atom desorption by electronic excitation with laser light. A realistic surface potential from which the atoms escape and nonlocal optical effects are taken into account. The latter introduce additional absorption channels by the formation of electron-hole pairs in the surface layer of the particle which relax into antibonding states before desorption occurs. Finally, the mechanism is discussed in the light of similar phenomena observed for thin metal films. Possibilities for future work are outlined. © 1993 The American Physical Society Y1 - 1993 U6 - https://doi.org/10.1103/PhysRevB.48.17463 ER - TY - JOUR A1 - Götz, T. A1 - Hoheisel, W. A1 - Träger, F. A1 - Vollmer, Michael T1 - Interplay between collective and single electron excitations in large metal clusters JF - In: Zeitschrift für Physik / D 26 (1993), 267-269 Y1 - 1993 ER - TY - CHAP A1 - Vollmer, Michael A1 - Kreibig, U. T1 - Collective excitations of large metal clusters T2 - In: Nuclear physics concepts in the study of atomic cluster physics : proceedings of the 88th W.-E.-Heraeus-Seminar, held at Bad Honnef, FRG, 26 - 29 November 1991 / R. Schmidt ... (ed.). - Berlin [u.a.] : Springer, 1992. - (Lecture notes in physics ; Vol. 404). - ISBN 3-540-55625-7 ; 0-387-55625-7. - S. 266-276 N2 - Studies of the evolution of the optical properties of metal clusters as a function of size have gained considerable attention in the last few years. One theoretical approach starts from large metal clusters, which can be described by classical electrodynamics, provided the dielectric functions of the clusters are known. the resulting resonant features in the absorption spectra are commonly called surface plasmons and are collective excitations of the electron system.The present paper discusses the electrodynamic (Mie) theory for large clusters of different metals, also considering the range of validity of this approach towards smaller cluster sizes. More details can be found in an extended review on this topic which is to be published soon [1]. Y1 - 1992 U6 - https://doi.org/10.1007/3-540-55625-7_30 SP - 266 EP - 276 ER - TY - CHAP A1 - Möllmann, Klaus-Peter A1 - Pinno, Frank A1 - Vollmer, Michael T1 - Microscopic and high-speed thermal imaging: a powerful tool in physics R&D T2 - In: InfraMation proceedings Vol.10 (2009), 303-317 Y1 - 2009 SP - 303 EP - 317 ER - TY - CHAP A1 - Vollmer, Michael A1 - Möllmann, Klaus-Peter A1 - Pinno, Frank T1 - Cheese cubes, light bulbs, soft drinks: An unusual approach to study convection, radiation and size dependent heating and cooling T2 - In: InfraMation proceedings Vol. 9 (2008), p. 477-492 Y1 - 2008 SP - 477 EP - 492 ER - TY - CHAP A1 - Möllmann, Klaus-Peter A1 - Pinno, Frank A1 - Vollmer, Michael T1 - Night sky radiant cooling – influence on outdoor thermal imaging analysis T2 - In: InfraMation proceedings Vol. 9 (2008), 279-295 Y1 - 2008 SP - 279 EP - 295 ER - TY - CHAP A1 - Pinno, Frank A1 - Möllmann, Klaus-Peter A1 - Vollmer, Michael T1 - Thermography of window panes – problems, possibilities and troubleshooting T2 - In: InfraMation proceedings Vol. 9 (2008), 355-362 Y1 - 2008 SP - 355 EP - 362 ER - TY - JOUR A1 - Vollmer, Michael A1 - Gedzelman, Stanley David T1 - Simulating irradiance during lunar eclipses: the spherically Symmetric case JF - In: Applied Optics 47 (2008) 34, H52-61 N2 - Irradiance during total lunar eclipses is simulated using a pinhole model. The Moon is illuminated by direct sunlight that is refracted into the Earth’s shadow as it passes through the atmosphere at the terminator but is depleted by scattering by molecules, extinction by aerosol particles, absorption by ozone, and obstruction by clouds and elevated land. On a spherical, sea-level Earth, and a cloudless, molecular atmosphere with no ozone, the eclipsed Moon appears red and calculated irradiance at the center of the umbra is reduced by a factor of about 2400 from direct moonlight. Selective absorption mainly of light around 600 nm by stratospheric ozone turns the periphery of the umbra pale blue. Typical distributions of aerosol particles, ozone, mountains, and clouds around the terminator reduce irradiance by an additional factor of the order of 100. © 2008 Optical Society of America Y1 - 2008 U6 - https://doi.org/http://dx.doi.org/10.1364/AO.47.000H52 SP - H52 EP - H61 ER - TY - JOUR A1 - Gedzelman, Stanley David A1 - Vollmer, Michael T1 - Simulating irradiance and color during lunar eclipses using satellite data JF - In: Applied Optics 47 (2008) 34, pp. H149-H156 N2 - Irradiance and color during the total lunar eclipses of 2007 and 2008 are simulated using a ray tracing model that includes refraction, scattering by molecules, and observed or climatological distributions of aerosols, ozone, clouds, and topography around the terminator. Central portions of the umbra appear deep red for almost all eclipses due to preferential removal of short wavelengths in the spectrum of sunlight by scattering in the lower troposphere. The fringe of the umbra appears turquoise or blue due to selective removal of wavelengths around 600 nm by the Chappuis absorption bands of ozone in the stratosphere. Asymmetric distributions of clouds and aerosols, particularly for the 2008 eclipse, produce minimum calculated irradiance up to 17  arc min from the umbra center, while high ozone content over the arctic makes the northern edge of the umbra deepest blue. © 2008 Optical Society of America Y1 - 2008 U6 - https://doi.org/http://dx.doi.org/10.1364/AO.47.00H149 SP - H149 EP - H156 ER -