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  • 1
    Electronic Resource
    Electronic Resource
    Efficient adiabatic population transfer by two-photon excitation assisted by a laser-induced Stark shift (2000)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 113 (2000), S. 534-546 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We demonstrate and analyze a novel scheme for complete transfer of atomic or molecular population between two bound states, by means of Stark-chirped rapid adiabatic passage (SCRAP). In this two-laser technique a delayed-pulse laser-induced Stark shift sweeps the transition frequency between two coupled states twice through resonance with the frequency of the population-transferring coupling laser. The delay of the Stark-shifting pulse with respect to the pulse of the coupling-laser Rabi frequency guarantees adiabatic passage of population at one of the two resonances while the evolution is diabatic at the other. The SCRAP method can give a population-transfer efficiency approaching unity. We discuss the general requirements on the intensity and timing of the pulses that produce the Rabi frequency and, independently, the Stark shift. We particularly stress extension to a double-SCRAP technique, a coherent variant of stimulated emission pumping in the limit of strong saturation. We demonstrate the success of the SCRAP method with experiments in metastable helium, where a two-photon transition provides the Rabi frequency. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.481829
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  • 2
    Electronic Resource
    Electronic Resource
    Socioeconomic status is a risk factor for allergy in parents but not in their children (2000)
    Oxford BSL : Blackwell Science Ltd
    Clinical & experimental allergy 30 (2000), S. 0 
    Details
    ISSN: 1365-2222
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Allergic diseases are more prevalent in affluent countries, which has been attributed to life-style factors. Life-style habits may also differ between socioeconomic (SES) classes. The objective of this paper therefore was to evaluate if SES had an impact on the development of atopic disorders.〈section xml:id="abs1-2"〉〈title type="main"〉MethodsA total of 1314 German children were followed-up in an observational birth cohort study to 6 years of age. Parents filled in questionnaires, and had multi-allergen screening tests for sensitization. Indoor allergen concentrations were determined by ELISA. Children were examined regularly up to 6 years, specific serum IgE values were determined by CAP-Rast-Feia.〈section xml:id="abs1-3"〉〈title type="main"〉ResultsThe risk of aeroallergen sensitization (odds ratio 1.76; 95% CI 1.30–2.37), and the lifetime prevalence of hay fever (2.36; 1.76–3.17), and asthma (1.74; 1.08–2.80), but not of atopic dermatitis (AD: 0.90; 0.54–1.51) was elevated in parents of high compared to low SES. With high SES the risk of smoking in pregnancy (0.35; 0.23–0.51), in the home (0.31; 0.21–0.46), pet ownership (0.37; 0.26–0.55), high mite (0.42; 0.25–0.74), and high cat (0.38; 0.18–0.82) allergen concentration in house dust was reduced, but elevated for breastfeeding over more than 6 months (4.67; 2.9–7.48). In children, even after controlling for other risk factors, only the risk of AD from 3 to 6 years (2.42; 1.42–4.14) was elevated in families with high SES, but not of AD in infancy or of any other atopic disorder.〈section xml:id="abs1-4"〉〈title type="main"〉ConclusionsWhile parents of high SES have a higher prevalence of inhalative allergies, their favourable life-style prevents the development of atopic disorders in their children, except for AD beyond infancy.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2222.2000.00927.x
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  • 3
    Electronic Resource
    Electronic Resource
    Breastfeeding duration is a risk factor for atopic eczema (2002)
    Oxford, UK : Blackwell Science, Ltd
    Clinical & experimental allergy 32 (2002), S. 0 
    Details
    ISSN: 1365-2222
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Background The results of numerous studies on the influence of breastfeeding in the prevention of atopic disorders are often contradictory. One of the most important problems is confounding by other lifestyle factors.Objective The aim of the present study was to analyse the effect of any breastfeeding duration on the prevalence of atopic eczema in the first seven years of life taking into account other risk factors.Methods In an observational birth cohort study 1314 infants born in 1990 were followed-up for seven years. At 3, 6, 12, 18, 24 months and every year thereafter, parents were interviewed and filled in questionnaires, children were examined and blood was taken for in vitro allergy tests. Generalized Estimation Equations (GEE)-models were used to model risk factors for the prevalence of atopic eczema and for confounder adjustmentResults Breastfeeding was carried out for longer if at least one parent had eczema, the mother was older, did not smoke in pregnancy, and the family had a high social status. The prevalence of atopic eczema in the first seven years increased with each year of age (OR 1.05; 95% CI 1.01–1.09 for each year), with each additional month of breastfeeding (1.03; 1.00–1.06 for each additional month), with a history of parental atopic eczema (2.06; 1.38–3.08), and if other atopic signs and symptoms appeared, especially specific sensitization (1.53; 1.25–1.88), and asthma (1.41; 1.07–1.85). Although breastfeeding should be recommended for all infants, it does not prevent eczema in children with a genetic risk.Conclusion Parental eczema is the major risk factor for eczema. But in this study, each month of breastfeeding also increased the risk
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2222.2002.01274.x
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  • 4
    Electronic Resource
    Electronic Resource
    Washing feather and synthetic pillows (2000)
    Copenhagen : Munksgaard International Publishers
    Allergy 55 (2000), S. 0 
    Details
    ISSN: 1398-9995
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1034/j.1398-9995.2000.00770.x
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  • 5
    Electronic Resource
    Electronic Resource
    Prevalence of adverse reactions to food in Germany – a population study (2004)
    Oxford, UK : Munksgaard International Publishers
    Allergy 59 (2004), S. 0 
    Details
    ISSN: 1398-9995
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Objective:  A population study was performed to identify the prevalence of all kinds of adverse reactions to food.Methods:  In a representative cross-sectional survey performed in 1999 and 2000 in Berlin, 13 300 inhabitants of all ages were addressed by questionnaire. This questionnaire was answered by 4093 persons. All respondents mentioning any sign of food intolerance or the existence of allergic diseases (n = 2298) were followed up by telephone and, in case food intolerance could not be ruled out by patient history, were invited to attend to the clinic for personal investigation including double-blind, placebo-controlled food challenge tests (DBPCFC).Results:  The self-reported lifetime prevalence of any adverse reaction to food in the Berlin population (mean age 41 years) was 34.9%. Eight hundred and fourteen individuals were personally investigated according to the guidelines. The point prevalence of adverse reactions to food confirmed by DBPCFC tests in the Berlin population as a mean of all age groups was 3.6% (95% confidence interval [3.0–4.2%]) and 3.7% in the adult population (18–79 years, 95% confidence interval [3.1–4.4.%]). Two and a half percent were IgE-mediated and 1.1% non-IgE-mediated, females were more frequently affected (60.6%). Based on a statistical comparison with available data of adults from the nationwide German Health Survey from 1998, adverse reactions to food in the adult population of Germany (age 18–79) were calculated with 2.6% [2.1–3.2%]).Conclusions:  The study gives for the first time information about the point prevalence of both immunological and nonimmunological adverse reactions to food and underlines the relevance of this issue in public health. The data also show that an individualized stepwise approach including provocation tests is mandatory to confirm the diagnosis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1398-9995.2003.00403.x
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  • 6
    Electronic Resource
    Electronic Resource
    Improved molecular constants for the and states of NaH (2000)
    Springer
    The European physical journal 10 (2000), S. 247-257 
    Details
    ISSN: 1434-6079
    Keywords: PACS. 33.15.Mt Rotation, vibration, and vibration-rotation constants - 33.20.Kf Visible spectra
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract: Improved molecular constants for the and states of the NaH molecule are presented. NaH molecules are produced by reactive scattering of H and Na2 in a crossed beam experiment. High vibrational levels (6 9) of the NaH molecules are predominantly populated. Their excitation spectrum in the range has been measured using a new variant of Doppler spectroscopy. The transition frequencies involving the vibrational levels 2 8 in the and 6 9 in the state have been determined with an accuracy of better than . Using also previously published data a new set of molecular constants for the and state is derived. In particular, the vibrational dependence of the rotational constants B, D and H as well as some of v”-v' band origins for and is determined. The transition frequencies measured here or published previously are reproduced by these new coefficients with an accuracy of 0.1 cm-1 [rms value] with a maximum deviation of 0.4 cm-1. New RKR potential energy curves have been calculated up to the turning points of the levels v” = 9 in the state and v' = 25 in the state.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s100530050546
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  • 7
    Electronic Resource
    Electronic Resource
    Coherent population trapping involving Rydberg states in xenon probed by ionization suppression (2001)
    Springer
    The European physical journal 17 (2001), S. 113-123 
    Details
    ISSN: 1434-6079
    Keywords: PACS. 42.50.Hz Strong-field excitation of optical transitions in quantum systems; multi-photon processes; dynamic Stark shift – 32.80.Rm Multiphoton ionization and excitation to highly excited states (e.g., Rydberg states) – 32.10.Fn Fine and hyperfine structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract: We report the observation of pronounced coherent population trapping and dark resonances in Rydberg states of xenon. A weak two-photon coupling with radiation of = 250 nm is induced between the 5p6 1 S 0 ground state of xenon and state 5p 56p[1/2]0, leading to (2+1) resonantly enhanced three-photon ionization. The state 5p 56p[1/2]0 is strongly coupled by radiation with ≃ 600 nm to 5p 5 ns[J C]1 or 5p 5 nd[J C]1 Rydberg states with principal quantum numbers n in the range 18 ?n? 23 and with the rotational quantum number of the ionic core J C = 1/2 or J C = 3/2. The ionization is monitored through observation of the photoelectrons with an energy resolution ΔE = 150 meV which is sufficient to distinguish the ionization processes into the two ionization continua. Pronounced and robust dark resonances are observed in the ionization rate whenever is tuned to resonance with one of the ns- or nd-Rydberg states. The dark resonances are due to efficient population trapping in the atomic ground state 5p6 1 S 0 through the suppression of excitation of the intermediate state 5p 56p[1/2]0. The resolution is sufficient to resolve the hyperfine structure of the ns-Rydberg levels for odd xenon isotopes. The hyperfine splitting does not vary significantly with n in the given range. Results from model calculations taking the natural isotope abundance into account are in good agreement with the observed spectral structures. Pronounced dark resonances are also observed when the dressing radiation field with is generated from a laser with poor coherence properties. The maximum reduction of the ionization signal clearly exceeds 50%, a value which is expected to be the maximum, when the dip is caused by saturation of the transition rate between the intermediate and the Rydberg state due to incoherent radiation. This work demonstrates the potential of dark resonance spectroscopy of high lying electronic states of rare gas atoms.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s100530170044
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  • 8
    Electronic Resource
    Electronic Resource
    Analytical study of four-wave mixing with large atomic coherence (2003)
    Springer
    The European physical journal 23 (2003), S. 167-180 
    Details
    ISSN: 1434-6079
    Keywords: PACS. 42.50.Gy Effects of atomic coherence on propagation, absorption, and amplification of light – 42.65.Ky Harmonic generation, frequency conversion – 32.80.Qk Coherent control of atomic interactions with photons
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract: Four-wave mixing in resonant atomic vapors based on maximum coherence induced by Stark-chirped rapid adiabatic passage (SCRAP) is investigated theoretically. We show the advantages of a coupling scheme involving maximum coherence and demonstrate how a large atomic coherence between a ground and an highly excited state can be prepared by SCRAP. Full analytic solutions of the field propagation problem taking into account pump field depletion are derived. The solutions are obtained with the help of an Hamiltonian approach which in the adiabatic limit permits to reduce the full set of Maxwell-Bloch equations to simple canonical equations of Hamiltonian mechanics for the field variables. It is found that the conversion efficiency reached is largely enhanced if the phase mismatch induced by linear refraction is compensated. A detailed analysis of the phase matching conditions shows, however, that the phase mismatch contribution from the Kerr effect cannot be compensated simultaneously with linear refraction contribution. Therefore, the conversion efficiency in a coupling scheme involving maximum coherence prepared by SCRAP is high, but not equal to unity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1140/epjd/e2003-00029-5
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  • 9
    Electronic Resource
    Electronic Resource
    Nonlinear Hanle effect in Cs vapor under strong laser excitation (2002)
    Springer
    The European physical journal 21 (2002), S. 63-71 
    Details
    ISSN: 1434-6079
    Keywords: PACS. 32.80.Bx Level crossing and optical pumping – 32.80.Qk Coherent control of atomic interactions with photons – 42.50.Gy Effects of atomic coherence on propagation, absorption, and amplification of light
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract: We report results of a theoretical and experimental study of the ground state nonlinear Hanle effect under strong laser excitation. It is shown that besides the well-known zero-magnetic field suppression of absorption on F g = F→F e = F - 1 transitions caused by population trapping, an optical pumping induced enhanced absorption occurs on F g = F→F e = F + 1 transitions for small B-fields. The latter effect becomes more pronounced for high F values. The experiment with atomic vapor of Cs (D2 line, F g = 4) confirms an increase of the spectrally unresolved fluorescence yield at zero magnetic field and 600 mW/cm2 laser intensity by 9% or 42%, when excitation occurs with linearly or circularly polarized light, respectively. The results of the experiment agree with numerical simulation studies using equations of motion for a density matrix.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1140/epjd/e2002-00178-y
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  • 10
    Electronic Resource
    Electronic Resource
    Efficient population transfer by delayed pulses despite coupling ambiguity (2000)
    Springer
    The European physical journal 8 (2000), S. 443-449 
    Details
    ISSN: 1434-6079
    Keywords: PACS. 42.50.Hz Strong-field excitation of optical transitions in quantum systems; multi-photon processes; dynamic Stark shift - 32.80.Wr Other multiphoton processes - 32.80.Bx Level crossing and optical pumping
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract: In traditional schemes of multilevel multilaser excitation, each laser pulse interacts with only one pair of states, and the rotating wave approximation (RWA) is applicable. Here we study the population transfer process in a three-state system when each of the two lasers interacts with each of the pair of states and when the Rabi frequencies characterizing the interaction strengths of the system are comparable to or larger than the difference of the transition frequencies. We show that complete and robust population transfer is possible under conditions more general than those hitherto considered necessary for stimulated Raman adiabatic passage (STIRAP) or for successive pulses. Using adiabatic Floquet theory we show that successful population transfer can be interpreted as adiabatic passage by means of a transfer state which connects the initial and final states. The Floquet picture offers a convenient interpretation of the population transfer as accompanied by multiple absorption of photons from or emission into the laser fields.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s100530050054
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