The Buffer Gas Beam: An Intense, Cold, and Slow Source for Atoms and Molecules

Beams of atoms and molecules are stalwart tools for spectroscopy and studies of collisional processes. The supersonic expansion technique can create cold beams of many species of atoms and molecules. However, the resulting beam is typically moving at a speed of 300-600 m/s in the lab frame, and for a large class of species has insufficient flux (i.e. brightness) for important applications. In contrast, buffer gas beams can be a superior method in many cases, producing cold and relatively slow molecules in the lab frame with high brightness and great versatility. There are basic differences between supersonic and buffer gas cooled beams regarding particular technological advantages and constraints. At present, it is clear that not all of the possible variations on the buffer gas method have been studied. In this review, we will present a survey of the current state of the art in buffer gas beams, and explore some of the possible future directions that these new methods might take

Molecular excitation in the Interstellar Medium: recent advances in collisional, radiative and chemical processes

We review the different excitation processes in the interstellar mediumComment: Accepted in Chem. Re

Observational Astronomy Research at a Primarily Undergraduate Institution

Over the past two decades there has been explosive growth in the number of undergraduate students participating in research across a variety of disciplines and at a range of institutions from community colleges to research universities. The benefits of undergraduate research to the student have been well documented, and include gains in learning, such as concept mastery and problem solving skills, increased retention in the major field, and greater interest in and preparation for graduate study. Faculty and their institutions also benefit from the increased role of undergraduate research through increased faculty satisfaction, curricular innovation, and recruitment of motivated and engaged students (Russell et al. 2007). Indeed, tenure and promotion decisions for faculty are increasingly dependent upon evidence of involving undergraduates in meaningful research

Bubble sources of the Knudsen sea noise spectra

Single coherent bubble contributions to the incoherent underwater noise of spilling breakers have been studied in an anechoic laboratory facility. The waves are generated by a plunger, they propagate 17 m along a 1.2×1.2‐m water waveguide, and ‘‘spill’’ and create bubbles at the surface of a 3×3×3‐m anechoic cube of water. Several species of bubbles have been identified. In general, they act as transient dipoles of duration from 2 to several milliseconds, with peak axial source strength of the order of tenths of pascals, at 1 m. The noise is emitted when the bubble is within hundreds of micrometers or a few millimeters of the surface. Bubbles were observed in the 2 decades of frequency from 500 to 50 000 Hz. The average of the individual bubble events yielded a spectrum that slopes at about 5 dB/oct from 1 to 20 kHz, the same as the Knudsen wind noise spectra at sea. The magnitude of the laboratory breaker noise during continual wave‐breaking events was approximately 80 dB re: 1 μ Pa2/Hz at 1 kHz, which is essentially the same as observed during the continual bubble production that occurs with very high winds at sea. The reasons for this agreement are discussed

EXTENSION OF TIME-RESOLVED DOUBLE RESONANCE STUDIES OF ROTATIONAL ENERGY TRNASFER TO AN OBLATE SYMMETRIC ROTOR

Author Institution: Department of Physics, Duke University; Physics Division, U.S. Army Research OfficeTime-resolved double resonance spectroscopy is a powerful technique for studying intramolecular energy transfer mechanisms. Previous studies of rotational energy transfer in the prolate symmetric tops $CH_{3} F$ and $CH_{3} Cl$ have culminated in a quantitative and predictive model for rovibrational relaxation in these molecules which reduces the inherent complexity of the problem to only a small number of adjustable parameters. In the oblate symmetric top $CDF_{3}$, the spacing between K levels is much closer than the spacing between J levels, while for $CH_{3}F$ and $CH_{3} Cl$ the opposite is true. The goal of the current study is to understand exactly what effect this has on the relative importance of the pathways for rovibrational relaxation in $CDF_{3}$, because it can provide a stringent test both of the existing model and of our current state of understanding of energy transfer mechanisms in polyatomic molecules. Recent experimental results will be presented

THE VARIABLE TEMPERATURE PRESSURE BROADENING AND LINE SHIFT OF CO AND HDO IN COLLISION WITH HELIUM

Author Institution: Department of Physics, The Ohio State UniversityPressure broadening and line shift cross sections for the 1$\leftarrow$0 and 2$\leftarrow$1 rotational transitions of carbon monoxide (CO) in collision with Helium (He) have been measured between 1 and 600 K. Measurements below 30 K were made using the collisional cooling technique, while measurements at higher temperatures were made in an equilibrium cell. The experimental apparatus and techniques employed in the study are described. The data are compared with theoretical predictions, and the significant differences between predictions based on the best available potential energy surface and the experimental results are discussed. Recent studies of the pressure broadening and line shifting of the $1_{10}\leftarrow1_{11}$ rotational transition of deuterated water (HDO) in collision with He will also be presented

THE VARIABLE TEMPERATURE PRESSURE BROADENING SPECTRUM OF CH3FCH_{3} F OF HELIUM

Author Institution: Department of Physics, The Ohio State UniversityA system has been developed which has allowed us to measure the helium pressure broadening parameters of $H_{2}S$ and $CH_{3}F$ between approximately 1K and 100K. In combination with other experimental systems, this has allowed measurements over a 1K to 1000K range. This range is wide enough to clearly observe the transition from the high temperature semiclassical regime in which the physics of the collision is properly described by Anderson-like theories to a low temperature regime in which new phenomena associated with quasibound states require a more complete quanmm mechanical description. New results for $CH_{3}F$ helium broadening will be discussed. Some comparisons will be made with measurements of previous experiments and with other molecular systems. The apparatus will be described as will experimental results and their relationship theoretical predictions