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Precision spectroscopy of simple, calculable molecules has become an important tool to compare experiments with theory in an effort to test our understanding of the fundamental laws of physics. For this purpose, we have measured the E F 1 Σ g + (v ′ = 0 , N ′ = 0) ← X 1 Σ g + (v ″ = 0 , N ″ = 0) transition frequency of molecular deuterium ( D 2 ) with unprecedented accuracy. We use Ramsey-Comb spectroscopy at deep-ultraviolet wavelengths (201 nm) with a two-photon, Doppler-free interrogation scheme. The resulting transition frequency is f = 2 , 981 , 779 , 227 , 578 (19) kHz. The 1-σ uncertainty of 19 kHz represents an improvement of more than two orders of magnitude compared to the best previous measurement. In this paper, we give an extensive description of our methods and the experimental apparatus that we employed. Particular attention is given to aspects that we recently improved, such as the frequency comb laser system, the method of signal recording, and the cryogenic D 2 molecular beam apparatus. In combination with future measurements of the ionisation energy of the EF state, our measurement paves the way for an improved determination of the ground state ionisation and dissociation energy of molecular deuterium. [ABSTRACT FROM AUTHOR]

Surface heating and cooling systems are gaining more and more importance in building energy technology. In order to implement these systems not only on the floor but also on the ceilings and walls, the thermodynamic requirements are supplemented by constructional requirements. In order to fulfil these requirements, the use of open-cell porous metals for such systems will be investigated in more detail. In addition to the design and manufacturing challenges, a large number of numerical and experimental investigations on test samples are also necessary. These investigations are described and explained in more detail in the following article.

The following article describes an extract of the results of experimental investigations on the topic of thermal comfort as a function of radiation asymmetry. The investigations were carried out in the climate chamber [1, 2] of the TU Dresden with the help of subjects. The radiation asymmetry was imprinted by subdividing the climate chamber into two vertically superimposed half-rooms, one of which was heated and the other cooled. In this way, 46 experiments on the heating or cooling ceiling were carried out. The measurement results show an inseparable link between the radiation asymmetry, the vertical air temperature difference and the air velocity. The subject assessed the room climate much more negatively than the ISO 7730 [3] would predict according to the state of the art.

Currently available energetic evaluation methods for heat pump and micro-CHP systems lead to results which partly deviate strongly from field measurements. A new evaluation method based on the Hardware-in-the-Loop concept was therefore developed and tested in a research project. The method employs representative days. A procedure for determining the representative days is presented. The functionality of the concept could be proven in a round robin test and the energetic key figures can be confirmed by values from field measurements values.

Ab initio calculations of the energy level structure of H 2 + that include relativistic and radiative corrections to nonrelativistic energies and the diagonal part of the hyperfine interaction have predicted the existence of four bound rovibrational levels [(v = 0, N = 0 − 2) and (v = 1, N = 0)] of the first electronically excited ( A + Σ u + 2 ) state of H 2 + , the (v = 1, N = 0) level having a calculated binding energy of only Eb = 1.082 219 8(4)·10−9 Eh and leading to an extremely large scattering length of 750(5) a0 for the H+ + H collision [J. Carbonell et al., J. Phys. B: At., Mol. Opt. Phys. 37, 2997 (2004)]. We present an investigation of the nonadiabatic coupling between the first two electronic states ( X + Σ g + 2 and A + Σ u + 2 ) of H 2 + induced by the Fermi-contact term of the hyperfine-coupling Hamiltonian. This interaction term, which mixes states of total spin quantum number G = 1/2, is rigorously implemented in a close-coupling approach to solve the spin-rovibronic Schrödinger equation. We show that it mixes states of gerade and ungerade electronic symmetry, that it shifts the positions of all weakly bound rovibrational states of H 2 + , and that it affects both the positions and widths of its shape resonances. The calculations demonstrate that the G = 1/2 hyperfine component of the A+ (v = 1, N = 0) state does not exist and that, for G = 1/2, the s-wave scattering lengths of the H+ + H(1s) collision are −578(6) a0 and −43(4) a0 for the F = 0 and F = 1 hyperfine components of the H(1s) atom, respectively. The binding energy of the G = 3/2 hyperfine component of the A+ (v = 1, N = 0) state is not significantly affected by the hyperfine interaction and the corresponding scattering length for the H+ + H(1s, F = 1) collision is 757(7) a0. [ABSTRACT FROM AUTHOR]

The electron affinity of the deuterium atom has been determined to be 6086.81(27) cm−1 from a measurement of the difference between the D+ + H− and H+ + D− ion-pair dissociation energies and a thermochemical cycle involving the electron affinity of H and the ionization energies of H and D. Heavy-Rydberg states and the ion-pair dissociation thresholds of HD were accessed with good efficiency using a three-photon excitation sequence through the B Σ u + 1 ( v = 22, N = 1) and H ¯ Σ g + 1 ( v = 9, N = 0) intermediate levels and the threshold positions were determined using the method of threshold-ion-pair-production spectroscopy. [ABSTRACT FROM AUTHOR]

We report on the measurement and analysis of photoionisation, mass-analysed-threshold-ionisation and pulsed-field-ionisation zero-kinetic-energy photoelectron spectra of HD in the vicinity of the dissociative-ionisation thresholds H + + D(1s) + e − and H(1s) + D + + e − . The spectra were recorded via the v = 11 − 13 vibrational levels of the H ¯ and B ¯ outer wells of the H H ¯ 1 Σ g + and B ′ ′ B ¯ 1 Σ u + states and provide information on the weakly bound levels of the X + 2 Σ g + ground state of HD + with vibrational quantum numbers v + = 16 − 21 and rotational angular-momentum quantum numbers N + = 0 − 10. The spectra also reveal for the first time shape and Feshbach resonances of HD + located energetically above the H + + D(1s) dissociation limit. The structure and dissociation dynamics of the H ¯ and B ¯ states of HD and of the X + 2 Σ g + and A + 2 Σ u + states of HD + near the dissociation thresholds are strongly influenced by the g/u-symmetry breaking caused by the nuclear-mass asymmetry. [ABSTRACT FROM AUTHOR]

Transitions from selected nd Rydberg states of H2 to n'p/f Rydberg series converging on the lowest two (N+ = 0 and 2) rotational levels of the X+ ²Sg+ (v + = 0) ground state of para-H2+ have been measured in the range 1-7.4 THz using a laser-based, pulsed, narrow-band source of submillimeter-wave radiation. The analysis of the spectra by multichannel quantum-defect theory (MQDT) has allowed a complete interpretation of the fine structures of the Rydberg series and their dependence on the principal quantum number. The extrapolation of the series to their limits with MQDT has enabled the determination of the first rotational interval of para-H2+, which is 174.236 71(7) cm-1 (5 223 485.1(2.3) MHz). [ABSTRACT FROM AUTHOR]

Transitions from selected nd Rydberg states of H2 to n'p/f Rydberg series converging on the lowest two (N+ = 0 and 2) rotational levels of the X+ ²Sg+ (v + = 0) ground state of para-H2+ have been measured in the range 1-7.4 THz using a laser-based, pulsed, narrow-band source of submillimeter-wave radiation. The analysis of the spectra by multichannel quantum-defect theory (MQDT) has allowed a complete interpretation of the fine structures of the Rydberg series and their dependence on the principal quantum number. The extrapolation of the series to their limits with MQDT has enabled the determination of the first rotational interval of para-H2+, which is 174.236 71(7) cm-1 (5 223 485.1(2.3) MHz). [ABSTRACT FROM AUTHOR]

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The term values of rovibrational levels of the GK 1Σ+g and H 1Σ+g states of H2 have been measured with absolute and relative accuracies down to 10−4 cm−1 (≈3 MHz) and 10−6 cm−1 (≈30 kHz), respectively, by measuring transitions to long-lived high-n Rydberg states using single-mode cw laser radiation and a collimated supersonic beam of cold H2 molecules. The term values are compared with those determined in earlier experimental and theoretical investigations and the comparison points at discrepancies and a need for improved theoretical treatments of nonadiabatic, relativistic and radiative corrections for these states. The lifetimes of several low-lying rovibrational levels of the GK, H and I+ 1Πg states have been determined in pump–probe experiments. These lifetimes reveal a significant dependence on the electronic, vibrational and rotational excitation and also deviate from results obtained in earlier experimental and theoretical investigations. [ABSTRACT FROM AUTHOR]

Although the existence of quasibound rotational levels of the X+²S+g ground state of H+2 was predicted a long time ago, these states have never been observed. Calculated positions and widths of quasibound rotational levels located close to the top of the centrifugal barriers have not been reported either. Given the role that such states play in the recombination of H(1s) and H+ to form H+2, this lack of data may be regarded as one of the largest unknown aspects of this otherwise accurately known fundamental molecular cation. We present measurements of the positions and widths of the lowest-lying quasibound rotational levels of H+2 and compare the experimental results with the positions and widths we calculate using a potential model for the X+ state of H+2 which includes adiabatic, nonadiabatic, relativistic, and radiative corrections to the Born-Oppenheimer approximation. [ABSTRACT FROM AUTHOR]

Lead (Pb 2+ ) and hexavalent chromium (Cr 6+ ) are highly toxic pollutants with no safe exposure levels, posing significant health risks globally, especially in developing countries. Current detection methods for these metals are often complex and inaccessible, highlighting the urgent need for innovative approaches. In this study, we present a rapid, cost-effective colorimetric assay utilizing ascorbic acid-capped gold nanoparticles (AuNPs) for the selective detection of Pb 2+ and Cr 3+/6+ ions at levels recommended by regulatory bodies such as the WHO and EPA. The synthesis of our AuNPs was achieved by reducing gold(III) chloride with ascorbic acid, resulting in stable, negatively charged nanoparticles, as characterized by dynamic light scattering, UV-vis spectroscopy and high-resolution transmission electron microscopy. Our method demonstrated high sensitivity, with limits of detection (LOD) of 5.4 ± 0.25 ppb for Pb 2+ , and 6.3 ± 0.23 ppb for Cr 6+ , confirming specificity towards these ions in various water samples. The assay's efficacy was validated in real-world applications, including testing drinking water from multiple sources and assessing the performance of filtration systems. This straightforward assay offers a promising tool for monitoring water quality, enhancing public health initiatives and accessibility to critical environmental testing.

A compact frequency-doubled diode-pumped Nd:YAG master-oscillator power-amplifier laser system with programmable microsecond pulse length has been developed. Analog pulse shaping of the output from a single-frequency continuous-wave Nd:YAG oscillator, and subsequent amplification, allowed the generation of rectangular pulses with pulse lengths on the order of the Nd:YAG fluorescence lifetime. Temporally flat-top pulses of 1064 nm light with 520 mJ pulse energy, 2.6 kW peak power, and 200 μs duration, with linewidth below 10 kHz, were obtained at a repetition rate of 2 Hz. Second harmonic generation in a LBO crystal yielded pulses of 262 mJ and 1.3 kW peak power at 532 nm. The peak power can be maintained within 2.9% over the duration of the laser pulse, and long-term intensity stability of 1.1% was observed. The spatially flat-top beam at 1064 nm used in the amplifier is converted to a Gaussian beam at 532 nm with beam quality factor M 2  = 1.41(14) during the second harmonic generation. This system has potential as a pump source for Ti:sapphire, dye, or optical parametric amplifiers to generate tunable high-power single-frequency radiation for applications in precision measurements and laser slowing.

The term values of rovibrational levels of the GK 1Σ+g and H 1Σ+g states of H2 have been measured with absolute and relative accuracies down to 10-4 cm-1 (≈3 MHz) and 10-6 cm-1 (≈30 kHz), respectively, by measuring transitions to long-lived high-n Rydberg states using single-mode cw laser radiation and a collimated supersonic beam of cold H2 molecules. The term values are compared with those determined in earlier experimental and theoretical investigations and the comparison points at discrepancies and a need for improved theoretical treatments of nonadiabatic, relativistic and radiative corrections for these states. The lifetimes of several low-lying rovibrational levels of the GK, H and I+ 1Πg states have been determined in pump-probe experiments. These lifetimes reveal a significant dependence on the electronic, vibrational and rotational excitation and also deviate from results obtained in earlier experimental and theoretical investigations.