Hermann Harde

Hermann Harde
Helmut Schmidt University Hamburg

Dr. rer. nat.

About

102
Publications
21,868
Reads
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1,154
Citations
Additional affiliations
July 1971 - February 1975
Technische Universität Kaiserslautern
Position
  • Research Assistant
Description
  • Set-up of a 400 keV accelerator and time-of-flight experiments with fast ion beams after intracavity laser excitation

Publications

Publications (102)
Article
Full-text available
The widely used Global Historical Climatology Network (GHCN) monthly temperature dataset is available in two formats - non-homogenized and homogenized. Since 2011, this homogenized dataset has been updated almost daily by applying the "Pairwise Homogenization Algorithm" (PHA) to the non-homogenized datasets. Previous studies found that the PHA can...
Article
Full-text available
The widely used Global Historical Climatology Network (GHCN) monthly temperature dataset is available in two formats—non-homogenized and homogenized. Since 2011, this homogenized dataset has been updated almost daily by applying the “Pairwise Homogenization Algorithm” (PHA) to the non-homogenized datasets. Previous studies found that the PHA can pe...
Article
Full-text available
In order to evaluate how much Total Solar Irradiance (TSI) has influenced Northern Hemisphere surface air temperature trends, it is important to have reliable estimates of both quantities. Sixteen different estimates of the changes in Total Solar Irradiance (TSI) since at least the 19th century were compiled from the literature. Half of these estim...
Preprint
Full-text available
To evaluate the role of Total Solar Irradiance (TSI) on Northern Hemisphere (NH) surface air temperature trends it is important to have reliable estimates of both quantities. 16 different TSI estimates were compiled from the literature. 1/2 of these estimates are low variability and 1/2 are high variability. 5 largely-independent methods for estima...
Article
Full-text available
The Intergovernmental Panel on Climate Change assumes that the inclining atmospheric CO2 concentration over recent years was almost exclusively determined by anthropogenic emissions, and this increase is made responsible for the rising temperature over the Industrial Era. Due to the far reaching consequences of this assertion, in this contribution...
Article
Full-text available
We present detailed line-by-line radiation transfer calculations, which were performed under different atmospheric conditions for the most important greenhouse gases water vapor, carbon dioxide, methane, and ozone. Particularly cloud effects, surface temperature variations, and humidity changes as well as molecular lineshape effects are investigate...
Article
Climate scientists presume that the carbon cycle has come out of balance due to the increasing anthropogenic emissions from fossil fuel combustion and land use change. This is made responsible for the rapidly increasing atmospheric CO2 concentrations over recent years, and it is estimated that the removal of the additional emissions from the atmosp...
Conference Paper
Full-text available
We have studied the time response of molecules by observing the pulse reshaping of femtosecond THz-pulses propagating through polar vapors. By precisely modeling the pulse interaction with symmetric top molecules we derive detailed insight into this time response after an excitation. The measurements were performed by applying the powerful techniqu...
Article
We investigate the time response of molecular transitions by observing the pulse reshaping of femtosecond THz-pulses propagating through polar vapors. By precisely modeling the pulse interaction with the molecular vapors, we derive detailed insight into this time response after an excitation. The measurements, which were performed by applying the p...
Article
Full-text available
We present an advanced two-layer climate model, especially appropriate to calculate the influence of an increasing CO2-concentration and a varying solar activity on global warming. The model describes the atmosphere and the ground as two layers acting simultaneously as absorbers and Planck radiators, and it includes additional heat transfer between...
Book
Full-text available
Energie, die Basis unseres Lebens, war zusammen mit den dafür eingesetzten Ressourcen und dem Klima das Thema eines Symposiums am 8. November 2012 in Erlangen. In Deutschland werden die von der Politik gestellten Fragen zur langfristigen Energieversorgung und zum Klimawandel mit großem Eifer in der Öffentlichkeit diskutiert, zu denen, entgegen der...
Article
Full-text available
We investigate the interaction of infrared active molecules in the atmosphere with their own thermal background radiation as well as with radiation from an external blackbody radiator. We show that the background radiation can be well understood only in terms of the spontaneous emission of the molecules. The radiation and heat transfer processes in...
Article
Full-text available
The composition and concentration of exhaled volatile gases reflects the physical ability of a patient. Therefore, a breath analysis allows to recognize an infectious disease in an organ or even to identify a tumor. One of the most prominent breath tests is the 13C-urea-breath test, applied to ascertain the presence of the bacterium helicobacter py...
Conference Paper
The composition and concentration of exhaled volatile gases reflects the physical ability of a patient. Therefore, a breath analysis allows to recognize an infectious disease in an organ or even to identify a tumor. One of the most prominent breath tests is the 13C-urea-breath test, applied to ascertain the presence of the bacterium helicobacter py...
Article
Full-text available
We demonstrate the operation of a fast scanning laser system that was modified to improve and to increase the time resolution as well as spectral width for femtosecond timeresolved optical pump-probe or THz time-domain spectroscopy.
Article
Full-text available
Exhaled nitric oxide was of high interest in breath analyses in the past few years. After its first detection in human breath in 1991, numerous publications uncovered the role of NO and its relation to different diseases. A strong relationship between an asthmatic eosinophilic airway inflammation and an increased NO level is medically confirmed. In...
Conference Paper
Full-text available
Exhaled nitric oxide was of high interest in breath analyses in the past few years. After its first detection in human breath in 1991, numerous publications uncovered the role of NO and its relation to different diseases. A strong relationship between an asthmatic eosinophilic airway inflammation and an increased NO level is medically confirmed. In...
Article
We present a new detection scheme for carbon dioxide (CO2) based on a custom-made room temperature distributed feedback (DFB) diode laser at 2.7 μm, currently representing one of the lasers with the highest emission wavelength of its kind. The detector's especially compact and simple set-up is based on photoacoustic spectroscopy (PAS). This method...
Article
Full-text available
Medical breath tests are well established diagnostic tools, predominantly for gastroenterological inspections, but also for many other examinations. Since the composition and concentration of exhaled volatile gases reflect the physical condition of a patient, a breath analysis allows one to recognize an infectious disease in an organ or even to ide...
Article
Full-text available
The development of new radiation sources has a major impact on the progress of optical trace gas detection. Particularly distributed feedback (DFB) diode lasers have proven to be very useful devices for spectroscopic sensors due to their spectral purity, direct modulation via the injection current, their small size and low acquisition cost. In this...
Conference Paper
Full-text available
Ziel unserer Untersuchungen ist es, einen auf photoakustischer Spektroskopie basierenden Sensor für Stickstoffmonoxid (NO) zur Asthmadiagnose zu entwickeln. Als Anregungsquelle wird ein gepulster DFB-Quantenkaskadenlaser verwendet, der bei Raumtemperatur betrieben wird. Es wurden Untersuchungen am Grundvibrationsübergang 1-0 von NO bei einer Wellen...
Article
Full-text available
This paper presents a process to manufacture all-polymer field effect transistors in a bottom gate configuration where all electrodes – including the gate electrode – are patterned using an excimer laser in combination with a scanning unit. This technique yields channel lengths of 10 μm between the source and the drain electrodes. Being a combinati...
Conference Paper
Full-text available
We present a program (MolExplorer), which uses the HITRAN04 database to compute and display molecular spectra on a PC Windows platform. Within seconds it provides survey spectra from mm-waves up to the ultraviolet as well as selected parts with highest spectral resolution to model the attenuation of radiation in the atmosphere or under laboratory c...
Conference Paper
Full-text available
We presented an isotope-selective detection scheme for CO2 based on a custom-made room temperature DFB-diode laser at 2.7 μm, currently representing the laser with the highest emission wavelength of its kind. The simple photoacoustic sensor enables very high detection sensitivities for 12CO2 and 13CO2 in the ppb range. The carefully selected spectr...
Article
Full-text available
We present a new detection scheme for carbon dioxide(CO2) based on a custom-made room temperature distributed feedback (DFB) diode laser at 2.7 mum, currently representing the laser with the highest emission wavelength of its kind. The detector's especially compact and simple set-up is based on photoacoustic spectroscopy (PAS). This method makes us...
Conference Paper
We present a new detection scheme for carbon dioxide(CO2) based on a custom-made room temperature distributed feedback (DFB) diode laser at 2.7 μm, currently representing the laser with the highest emission wavelength of its kind. The detector's especially compact and simple set-up is based on photoacoustic spectroscopy (PAS). This method makes use...
Article
Development of new optical sensor technologies has a major impact on the progression of diagnostic methods. Specifically, the optical analysis of breath is an extraordinarily promising technique. Spectroscopic sensors for the non-invasive ¹³C-breath tests (the Urea Breath Test for detection of Helicobacter pylori is most prominent) are meanwhile we...
Article
Full-text available
Development of new optical sensor technologies has a major impact on the progression of diagnostic methods. Of the permanently increasing number of non-invasive 13C-breath tests, the Urea Breath Test for detection of Helicobacter pylori is the most prominent. However, many recent developments go beyond gastroenterological applications. We present a...
Article
Full-text available
The detection sensitivity of photoacoustic sensors strongly depends on the design of the sample cell. It can be considerably improved by taking advantage of acoustical resonances of the measuring chamber. In order to optimize a photoacoustic system, it is key to precisely understand the distribution of pressure in the sample cell. Therefore, we hav...
Conference Paper
Development of new optical sensor technologies has a major impact on the progression of diagnostic methods. Specifically, the optical analysis of breath is an extraordinarily promising technique. Spectroscopic sensors for the non-invasive 13C-breath tests (the Urea Breath Test for detection of Helicobacter pylori is most prominent) are meanwhile we...
Conference Paper
The detection sensitivity of a photoacoustic gas sensor strongly depends on the design of the sample cell [1]. It can be considerably improved by taking advantage of acoustical cell resonances, i.e., the radiation is modulated at a frequency equivalent to an acoustical mode of the measuring chamber. Most contemporary PA systems enhance their signal...
Conference Paper
Full-text available
The photoacoustic effect is based on the resonant absorption of light by a sample and the transfer of the excitation energy into thermal energy via inelastic collisions. A modulated irradiation of the sample causes periodic pressure variations that can be detected by a microphone and measured using lock-in technique. The detection sensitivity of Ph...
Article
Full-text available
We have developed a photoacoustic spectrometer based on a distributed feedback (DFB) diode laser. The single-mode emission of the laser can be tuned continuously over 700 GHz enabling the precise determination of absorption line parameters. Our experiments were performed on the rotational lines P2 and P3 of the vibrational transition 2-0 (overtone)...
Article
Full-text available
The development of new optical sensor technologies has a major impact on the progress of diagnostic methods. Of the permanently increasing number of non-invasive breath tests, the 13C-Urea Breath Test (UBT) for the detection of Helicobacter pylori is the most prominent. However, many recent developments, like the detection of cancer by breath test,...
Conference Paper
Full-text available
In einem hier erstmalig beschriebenen Forschungsprojekt der Universität der Bundeswehr Hamburg wird die Photoakustische Spektroskopie (PAS) mit einzelmodigen Diodenlasern bei Raumtemperatur eingesetzt, um mit Hilfe eines neuen Auswerteverfahrens eine verbesserte Analyse von Atemproben zu ermöglichen [1,2].
Article
We have developed a photoacoustic spectrometer based on a fast responding Planckian radiator. This promising radiation source represents a matrix of 35 tiny resistors (0.500mm×0.357 mm) that emit their peak power in the mid-infrared wavelength region and that can be directly modulated via their current. It enables a simple, compact and robust detec...
Article
Weak or sensitive surfaces like pigment lacquer, finishing varnish, art paintings or plastics are much more precarious to clean due to the danger of a partial or complete damage of the layer which may have a protective function or artistic merit. So it is essential only to remove the contamination itself or, if necessary, the contamination together...
Conference Paper
The development of new optical sensor technologies has a major impact on the progress of diagnostic methods. Of the permanently increasing number of non-invasive breath tests, the 13C-Urea Breath Test (UBT) for the detection of Helicobacter pylori is the most prominent. However, many recent developments, like the detection of cancer by breath test,...
Conference Paper
Die Absorption und Dispersion von Ammoniak-Gasen im Terahertz-Frequenzbereich wurde für Temperaturen zwischen 20-120 C und für Drücke von 100-3000 hPa in einer Gaszelle gemessen. Mit Hilfe der zeitaufgelösten Terahertz-Spektroskopie, die sich durch ihre hohe Empfindlichkeit und Dynamik in diesem Spektralbereich besonders auszeichnet, konnte erstmal...
Article
We use the technique of terahertz time-domain spectroscopy to experimentally and theoretically study the absorption and the dispersion of ammonia vapor. Our measurements show small deviations from the rotation-inversion spectrum which originate from transitions in the ν2 hot band and from the (NH3)2 dimer. We investigate the molecular tunneling in...
Article
Summary form only given. We present a device developed for cleaning of superficial adherent impurities by removal of only thin films of a surface layer. This cleaning is of interest for a multitude of objects in industry or arts. Basically the intention is the removal of contaminations consisting of dust and environmental impacts which are deposite...
Conference Paper
We use the technique of terahertz time-domain spectroscopy to experimentally and theoretically study the absorption and dispersion of ammonia vapor. Our measurements show small deviations from the rotation-inversion spectrum which originate from transitions in the ν2 hot band and from the (NH3)2 dimer. We investigate the molecular tunneling in ammo...
Conference Paper
We report on the observation of dark resonances originating from the characteristic motion of Paul trapped ions and we present measurements of the ion cloud distribution which at higher densities is found to form a "hollow ball". We discuss an expanded model for the motion and space distribution of ions in a large trap.
Article
Experiments show the applicability of the photoacoustic diode laser spectrometer as a compact detector for the sensitive monitoring of HF at atmospheric pressure. The modulation of the injection current allows the generation of a photoacoustic signal at the high resonance frequency of the cell and avoids coherent noise from a chopper or photoacoust...
Conference Paper
Summary form only given. Application of an ion trap as a frequency standard requires cooling of the ions or an accurate knowledge of the ion motion to compensate for frequency shifts due to the second-order Doppler effect. In this contribution we report on the observation of atomic coherence effects, which originate from the characteristic motion o...
Article
Summary form only. We present investigations aiming on the removal of only thin films of a surface layer for cleaning the top lacquer or paint layer together with superficial adherent impurities without destroying the protective function of the layer of the underlying structure. For an automatic operation and fast cleaning of plane surfaces we set...
Article
Full-text available
We use the technique of terahertz time-domain spectroscopy to investigate the absorption and dispersion of spectrally dense methyl halide vapors, particularly in the low- and high-frequency spectral wings. For the first time to our knowledge, it is possible to observe essentially zero-frequency absorption resulting from molecular tunneling between...
Conference Paper
Full-text available
We have developed a photoacoustic spectrometer using a distributed-feedback-laserdiode. The laser can be tuned continuously over 700 GHz allowing both sensitive concentration measurements and the precise measurement of absorption line parameters.
Article
Via terahertz (THz) coherent transients and THz time-domain spectroscopy, we have measured the far-wing absorption line profile of the ensembles of collision-broadened ground state rotational lines of methyl bromide, methyl chloride, and methyl fluoride vapors out to more than 200 line widths from resonance, corresponding to frequency offsets as mu...
Conference Paper
Full-text available
Es wurde ein photoakustisches Laserdioden-Spektrometer für die Obertonspektroskopie und den empfindlichen Nachweis von molekularen Spurengasen entwickelt. Eine InGaAsP-Distributed-Feedback-Laserdiode, die bei Raumtemperatur betrieben wird und deren einzelne longitudinale Mode über 700 GHz kontinuierlich durchstimmbar ist, diente dabei als Anregung...
Conference Paper
Full-text available
Es wurden Spektroskopische Untersuchungen an der Rotationslinie P3 des Vibrationsüberganges 2-0 von Fluorwasserstoff (HF) durchgeführt. Zur Anregung diente eine mittels Betriebsstrom und -temperatur durchstimmbare DFB-Laserdiode bei einer Wellenlänge von 1310 nm. Die Photoakustische Spektroskopie (PAS) wurde dabei der herkömmlichen Transmissionsspe...
Article
Pulse generation in birefringent fibers by four-wave mixing in the presence of Raman scattering is theoretically modeled by a set of coupled nonlinear Schrödinger equations that are solved numerically. We discuss phase matching in the positive group-velocity dispersion regime for the split-pump configuration, which places the parametric frequency s...
Article
Full-text available
Using the newly developed technique of THz time-domain spectroscopy, we have measured the far-wing absorption line profile of the ensemble of collision broadened ground state rotational lines of methylchloride vapor out to more than 200 linewidths from resonance, corresponding to frequency offsets as much as 5× the resonant frequency. On these far...
Article
Full-text available
A newly developed optoelectronic source for generating well-collimated beams of subpicosecond pulses of terahertz radiation was used to study coherent propagation effects in a spectrally thick medium of methyl chloride vapor. After the passage of the excitation pulse, we observe the subsequent emission of a coherent terahertz pulse train in the fre...
Conference Paper
Full-text available
Es wurden Untersuchungen zum gezielten Nachweis von 13CO2 durchgeführt. Das Ziel ist es, einen photoakustischen Detektor zu entwickeln, der es ermöglicht, sowohl die absolute 13CO2-Konzentration als auch das Verhältnis von 13CO2 zu 12CO2 zu bestimmen. Nachweisschemata mit Lasern werden diskutiert und einem Aufbau mit einer konventionellen Lampe geg...
Article
A newly developed optoelectronic beam system generating subpicosecond pulses of THz radiation was used for time-domain studies of N2O vapor. After the excitation the molecules were observed to radiate coherent transients on the free-induction decay originating from the periodic rephasing of coherently excited rotational absorption lines. Numerical...
Article
A new method for the measurement of motional frequencies and amplitudes of stored ions in a radio-frequency trap is presented. Ions oscillating in the trap potential and additionally subjected to a small magnetic field, undergo sublevel transitions between adjacent Zeeman states when their motional frequency is identical with the Larmor frequency i...
Article
Full-text available
Using a newly developed optoelectronic source of well-collimated beams of subpicosecond pulses of terahertz radiation to excite a N2O vapor cell, we have observed the subsequent emission from the vapor of a coherent pulse train extending as long as 1 ns. The individual subpicosecond terahertz pulses of the train are separated by 39.8 ps, correspond...
Article
We report the first study of coherent transients excited by ultrafast pulses of THz radiation. Using a newly developed optoelectronic source of well-collimated beams of subpicosecond pulses of THz radiation to excite N2O vapor, we have observed the subsequent emission from the vapor of coherent THz pulse trains extending to as long as 1 nsec. The o...
Article
Operation of a wavelength tunable fiber grating Raman laser working in the 1.1 m regime is demonstrated. The pumping mechanism utilizes the process of stimulated perpendicular Raman scattering, possible in fibers for which birefringence can compensate dispersion. A total tuning range of 40 nm with a minimum output pulse duration of 0.8 ps is achiev...
Article
Resonant laser excitation of Yb ions confined in an RF ion trap is found to result in perfect population trapping in the highly metastable 2F7/2 state. The lifetime of this level is measured to be greater than 8 d. Population and depopulation of this level under narrow- and broad-band laser excitation conditions is investigated, and its potentialit...
Article
Successful operation of a fiber grating Raman laser delivering pulses of 0.8 ps duration at a wavelength of 1.1 mum is presented. The pulses are generated with a novel method taking advantage of stimulated perpendicular Raman scattering in conjunction with dispersion compensation in a birefringent fiber.
Article
Nonlinear propagation effects in birefringent optical fibers are investigated and their implications for generating ultrashort light pulses in the IR are discussed. Stable compression of intense Nd:YAG laser pulses is obtained due to combined action of self-phase modulation, stimulated Raman scattering, and group-velocity dispersion. First operatio...
Article
Compression of intense Nd:YAG laser pulses by a fiber-grating compressor is investigated experimentally and theoretically. An increased stability of compressor operation in the Raman regime and a considerable further shortening of pulses with a compression factor of 130× is reported. A complete theoretical model of pulse compression is presented, i...
Article
A theoretical model of pulse propagation through single-mode fibres is presented taking into account the combined action of self-phase modulation, stimulated Raman-scattering and the group velocity mismatch between pump and Stokes pulses. Due to the walk-off of Stokes and laser light an asymmetric pump pulse depletion resulting in considerable resh...