REMPI Spectroscopy of HfF

The spectrum of electronic states at 30000--33000 cm$^{-1}$ in hafnium fluoride has been studied using (1+1) resonance-enhanced multi-photon ionization (REMPI) and (1+1$'$) REMPI. Six $\Omega' = 3/2$ and ten $\Pi_{1/2}$ vibronic bands have been characterized. We report the molecular constants for these bands and estimate the electronic energies of the excited states using a correction derived from the observed isotope shifts. When either of two closely spaced $\Pi_{1/2}$ electronic states is used as an intermediate state to access autoionizing Rydberg levels, qualitatively distinct autoionization spectra are observed. The intermediate state-specificity of the autoionization spectra bodes well for the possibility of using a selected $\Pi_{1/2}$ state as an intermediate state to create ionic HfF$^+$ in various selected quantum states, an important requirement for our electron electric dipole moment (eEDM) search in HfF$^+$.Comment: 11 pages, 8 figures, 1 tabl

Susceptibility to 5-aminolevulinic acid based photodynamic therapy in WHO I meningioma cells corresponds to ferrochelatase activity

5-Aminolevulinic acid (5-ALA) is a natural precursor of protoporphyrin IX (PpIX), which can be used as a photosensitizer in photodynamic therapy (PDT). Accumulation of PpIX in benign meningioma cells has been observed previously, its exploitation for PDT, however, was discouraged by inconsistent results. To evaluate PDT for benign meningiomas, we investigated PpIX synthesis in two human meningioma cell lines (HBL-52 and BEN MEN-1), their respective extracellular loss of PpIX and corresponding ferrochelatase (FECH) activity as well as their susceptibility to PDT. We demonstrated PpIX production after 5-ALA administration and minor loss to the extracellular space in both cell lines. However, significantly more (up two five times) PpIX was accumulated in BEN-MEN-1 as compared to HBL-52 cells. FECH activity was 2.7 fold higher in HBL-52 compared to BEN-MEN-1 cells and accordingly higher FECH levels could be shown in HBL-52 cells by western blot analysis. BEN MEN-1 cells were much more sensitive to PDT and cells could be almost completely killed by irradiation doses of 2 J cm-2, whereas HBL-52 showed only an insuffient response at this irradiation dose. We conclude that differences in intracellular PpIX concentrations between HBL-52 and BEN-MEN-1 benign menigioma cells were mainly due to differences in FECH activity and that these differences correspond to their susceptibility to 5-ALA induced PDT

High-precision laser spectrometer for multiple greenhouse gas analysis in 1 mL air from ice core samples

The record of past greenhouse gas composition from ice cores is crucial for our understanding of global climate change. Future ice core projects will aim to extend both the temporal coverage (extending the timescale to 1.5 Myr) and the temporal resolution of existing records. This implies a strongly limited sample availability, increasing demands on analytical accuracy and precision, and the need to reuse air samples extracted from ice cores for multiple gas analyses. To meet these requirements, we designed and developed a new analytical system that combines direct absorption laser spectroscopy in the mid-infrared (mid-IR) with a quantitative sublimation extraction method. Here, we focus on a high-precision dual-laser spectrometer for the simultaneous measurement of CH4, N2O, and CO2 concentrations, as well as d13C(CO2). Flow-through experiments at 5 mbar gas pressure demonstrate an analytical precision (1 sigma) of 0.006 ppm for CO2, 0.02‰ for d13C(CO2), 0.4 ppb for CH4, and 0.1 ppb for N2O, obtained after an integration time of 100 s. Sample–standard repeatabilities (1 sigma) of discrete samples of 1 mL STP (Standard Temperature and Pressure) amount to 0.03 ppm, 2.2 ppb, 1 ppb, and 0.04‰ for CO2, CH4, N2O, and d13C(CO2), respectively. The key elements to achieve this performance are a custom-developed multipass absorption cell, custom-made high-performance data acquisition and laser driving electronics, and a robust calibration approach involving multiple reference gases. The assessment of the spectrometer capabilities in repeated measurement cycles of discrete air samples – mimicking the procedure for external samples such as air samples from ice cores – was found to fully meet our performance criteria for future ice core analysis. Finally, this non-consumptive method allows the reuse of the precious gas samples for further analysis, which creates new opportunities in ice core science

A High-Precision Mid-Infrared Spectrometer for Ambient HNO₃ Measurements

Precise and accurate measurements of ambient HNO3 are crucial for understanding various atmospheric processes, but its ultra-low trace amounts and the high polarity of HNO3 have strongly hindered routine, widespread, direct measurements of HNO3 and restricted field studies to mostly short-term, localized measurement campaigns. Here, we present a custom field-deployable direct absorption laser spectrometer and demonstrate its analytical capabilities for in situ atmospheric HNO3 measurements. Detailed laboratory characterizations with a particular focus on the instrument response under representative conditions for tropospheric measurements, i.e., the humidity, spectral interference, changing HNO3 amount fractions, and air-sampling-related artifacts, revealed the key aspects of our method: (i) a good linear response (R2 > 0.98) between 0 and 25 nmol·mol−1 in both dry and humid conditions with a limit of detection of 95 pmol·mol−1; (ii) a discrepancy of 20% between the spectroscopically derived amount fractions and indirect measurements using liquid trapping and ion chromatography; (iii) a systematic spectral bias due to water vapor. The spectrometer was deployed in a three-week field measurement campaign to continuously monitor the HNO3 amount fraction in ambient air. The measured values varied between 0.1 ppb and 0.8 ppb and correlated well with the daily total nitrates measured using a filter trapping method

Compact and lightweight mid-infrared laser spectrometer for balloon-borne water vapor measurements in the UTLS

We describe the development, characterization, and first field deployments of a quantum cascade laser direct absorption spectrometer (QCLAS) for water vapor measurements in the upper troposphere and lower stratosphere (UTLS). The instrument is sufficiently small (30×23×11 cm3) and lightweight (3.9 kg) to be carried by meteorological balloons and used for frequent soundings in the UTLS. The spectrometer is a fully independent system, operating autonomously for the duration of a balloon flight. To achieve the required robustness, while satisfying stringent mass limitations, the concepts for optics and electronics have been fundamentally reconsidered compared to laboratory-based spectrometers. A significant enhancement of the mechanical and optical stability is achieved by integrating a newly designed segmented circular multipass cell which allows for 6 m optical path length in a very compact fashion. The H2O volume mixing ratio is retrieved by calibration-free evaluation of the spectral data, i.e., only relying on SI-traceable measurements and absorption line parameters. The open-path design reduces the risk of contamination and allows for fast response and thus high vertical resolution. Laboratory-based characterization experiments show an agreement within 2 % of reference measurements and a precision of 0.1 % under conditions comparable to the UTLS. The instrument successfully performed two balloon-borne test flights up to 28 km altitude. In the troposphere, the retrieved spectroscopic data show an excellent agreement with the accompanying measurements by a frost point hygrometer (CFH). At higher altitude, the quality of the spectral data remained unchanged, but outgassed water vapor within the instrument enclosure was hindering an accurate measurement of the atmospheric water vapor. Despite this limitation, these test flights demonstrated the operation of a compact laser spectrometer in the UTLS aboard a low-volume meteorological balloon, opening the perspective for future highly resolved, accurate, and cost-efficient soundings.ISSN:1867-1381ISSN:1867-854