ABSTRACT
The unique optical cycling efficiency of alkaline earth metal-ligand molecules has enabled significant advances in polyatomic laser cooling and trapping. Rotational spectroscopy is an ideal tool for probing the molecular properties that underpin optical cycling, thereby elucidating the design principles for expanding the chemical diversity and scope of these platforms for quantum science. We present a comprehensive study of the structure and electronic properties in alkaline earth metal acetylides with high-resolution microwave spectra of 17 isotopologues of MgCCH, CaCCH, and SrCCH in their 2Σ+ ground electronic states. The precise semiexperimental equilibrium geometry of each species has been derived by correcting the measured rotational constants for electronic and zero-point vibrational contributions calculated with high-level quantum chemistry methods. The well-resolved hyperfine structure associated with the 1,2H, 13C, and metal nuclear spins provides further information on the distribution and hybridization of the metal-centered, optically active unpaired electron. Together, these measurements allow us to correlate trends in chemical bonding and structure with the electronic properties that promote efficient optical cycling essential to next-generation experiments in precision measurement and quantum control of complex polyatomic molecules.
ABSTRACT
We report the first direct detection of ethyl radical in the pyrolysis of ethane. Observation of this vital intermediate was made possible in this extremely reactive environment by the use of a microreactor coupled with synchrotron radiation and photoelectron photoion coincidence (PEPICO) spectroscopy, despite its short lifetime and low concentration. Together with ab-initio master equation-calculated rates and fully coupled computational fluid dynamics simulations, our measurements show that even under the low pressures and short residence times in our experiment, ethyl formation can only be explained by bimolecular reactions; the most important is the catalytic attack of ethane by H atoms, which are then regenerated by decomposition of the nascent ethyl radicals. Our results complete the observation of all hypothesized intermediates in this industrially important process and highlight the need for further studies under additional conditions using similar methods to improve existing models and optimize process chemistries.
ABSTRACT
OBJECTIVE: Infectious diseases account for up to 43% of childhood hospitalizations. Given the magnitude of infection-related hospitalizations, we aimed to evaluate the effect of maternal smoking during pregnancy on the risk for long-term childhood infectious morbidity. STUDY DESIGN: This is a population-based cohort analysis comparing the long-term risk for infectious diseases, in children born to mothers who smoked during pregnancy versus those who did not. Infectious diseases were predefined based on International Classification of Diseases, Ninth Revision codes. Deliveries occurred between the years 1991 and 2014. RESULTS: A total of 246,854 newborns met the inclusion criteria; 2,986 (1.2%) were born to mothers who smoked during pregnancy. Offspring of smokers had significantly higher risk for several infectious diseases during childhood (upper respiratory tract, otitis, viral infections, and bronchitis) as well as increased risk for total infection-related hospitalizations (odds ratio = 1.5, 95% confidence interval [CI]: 1.3-1.7; p = 0.001). Cumulative incidence of infection-related hospitalizations was significantly higher in offspring of smokers (log-rank test, p = 0.001). Controlling for maternal age, diabetes, hypertensive disorders, and gestational age at index delivery, smoking remained an independent risk factor for infectious diseases during childhood (adjusted hazard ratio = 1.5, 95% CI: 1.3-1.6; p = 0.001). CONCLUSION: Intrauterine exposure to maternal smoking may create an environment leading to an increased future risk for long-term pediatric infectious morbidity of the offspring.