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Ball plasmoid discharges are a unique type of atmospheric-pressure plasma discharge with a lifetime on the order of a hundred milliseconds without attachment to a power source. These discharges are generated by a moderate current pulse over the surface of an aqueous electrolyte, and some consider the spherical plasmoid that results to bear some resemblance to ball lightning. This article presents the first analysis of the electrical properties of ball plasmoid discharges in a reversed-polarity configuration, i.e., with the central electrode serving as the anode rather than as the cathode. These experiments demonstrate that ball plasmoids can indeed be generated with either electrode polarity with similar observable properties. These results are contrary to what has previously been discussed in the literature and raise additional questions regarding formation mechanisms of ball plasmoids. Analysis of images and electrical measurements collected at various discharge energies show that two distinct processes occur during discharges with our circuitry and in this reversed-polarity configuration: the formation of spark channels between the anode and electrolyte, and the generation of streamers and a jet from the surface of the anode.

The molecular ion D 2 H + is an important species in cold interstellar environments and a key benchmark for ab initio calculations. We have measured 37 transitions in the ν 1 fundamental band using the sub-Doppler technique Noise Immune Cavity Enhanced Optical Heterodyne Velocity Modulation Spectroscopy. Using an optical frequency comb for accurate frequency calibration, the uncertainties for most transitions were improved by more than an order of magnitude. These new measurements lead to improved predictions of pure rotational transition frequencies which have not been observed by THz observatories or laboratory spectrometers.

We have performed sub-Doppler resolution rovibrational spectroscopy of the ν3 band of methane (12CH4) in the mid-infrared using an optical parametric oscillator in a double-pass configuration for saturated absorption. An optical frequency comb was used for absolute frequency calibration. We have measured 22 methane line centers ranging from the P(13) to R(10) transitions with a typical uncertainty of 0.40 MHz. These measurements improve previously known transition frequencies by at least an order of magnitude.

We report the first (to our knowledge) infrared emission spectra collected from water-based laboratory ball plasmoid discharges. A “ball plasmoid” results from a unique type of pulsed DC plasma discharge in which a sphere of plasma is seen to grow and eventually separate from a central electrode and last for a few hundred milliseconds without an external power source before dissipating. Typical recombination rates for plasmas at ambient conditions are on the order of a millisecond or less, however ball plasmoids have been observed to last a few hundred milliseconds, and there is no explanation in the literature that fully accounts for this large discrepancy in lifetime. The spectra are dominated by emission from water and from hydroxyl radical; PGOPHER was used to fit the experimental spectra to extract rotational temperatures for these molecules. The temperatures of the bending and stretching modes of H2O were determined to be 1900 ± 300 K and 2400 ± 400 K, respectively and the rotational temperature of OH was found to be 9200 ± 1500 K.

This paper analyzes the cost-effectiveness of converting the University of Dayton (UD) to a fully-electrified, renewably powered, carbon-neutral campus by 2025. The greenhouse gas (GHG) impact and 30-year lifecycle costs (LCC) of a scenario including four primary strategies for transitioning to carbon-neutrality were analyzed; scaling building energy efficiency was determined to reduce GHG emissions by 12% with $10 million LCC savings from business as usual, switching the campus fleet to electric vehicles would reduce GHG emissions by 0.4% with $2 million LCC savings, switching from on-site natural gas combustion to geothermal heat pumps would reduce GHG emissions by 15% with a $15.5 million LCC premium, and procuring renewable electricity through a power purchase agreement with a new-build renewable generator would eliminate the remaining 73% of GHG emissions with a $1.7 million LCC premium. In total, achieving a carbon-neutral campus would increase the 30-year LCC of UD’s energy systems by 2.4%, from $211.8 million to $216.9 million. This is likely a reasonable investment to consider, given the uncertainties in future commodity pricing, the potential of future regulatory mechanisms like carbon pricing that would internalize the social cost of carbon, and the urgent need to reduce global GHG emissions.

Ball lightning is a naturally occurring atmospheric event that has perplexed researchers for centuries, and there is to date no complete explanation (chemical, physical, or otherwise) as to why ball lightning behaves the way that it does. There has been considerable effort to try to both produce and measure the properties of ball lightning type discharges over recent years, and this collected work has begun to reveal some interesting physical and chemical phenomena. We are able to produce water-based plasma ball discharges using high-voltage equipment, and these self-contained plasmoids are considered to be similar to natural ball lightning. In this article we present the first mass spectrometric analysis of water-based ambient ball plasmoids. Using an extremely simple sampling technique, we were able to detect several chemical species within the interior of the plasmoid. Several molecules that are common to plasmas generated in air were observed in the mass spectra, such as [NO 2 ] + and [NO 3 ] + . More interestingly, we observed the protonated water clusters [(H 2 O) 2 H] + and [(H 2 O) 3 H] + , ammonia (NH 3 ) as a component of a copper cluster, and several anions. Furthermore, many species observed in the mass spectra are in the form of hydrated clusters.

The performance of sensitive spectroscopic methods in the mid-IR is often limited by fringing due to parasitic etalons and the background noise in mid-infrared detectors. In particular, the technique Noise Immune Cavity Enhanced Optical Heterodyne Velocity Modulation Spectroscopy (NICE-OHVMS), which is capable of determining the frequencies of strong rovibrational transitions of molecular ions with sub-MHz uncertainty, needs improved sensitivity in order to probe weaker transitions. In this work, we have implemented up-conversion detection with NICE-OHVMS in the 3.2 - 3.9 µm region to enable the use of faster and more sensitive detectors which cover visible wavelengths. The higher bandwidth enabled detection at optimized heterodyne frequencies, which increased the overall signal from the H3+ cation by a factor of three and was able to resolve sub-Doppler features which had previously overlapped. Also, we demonstrate the effectiveness of Brewster-plate spoilers to remove fringes due to parasitic etalons in a cavity enhanced technique. Together, these improvements reduced the instrument's noise equivalent absorption to 5.9×10sup-11/supcmsup-1/supHzsup-1/2/sup, which represents a factor of 34 improvement in sensitivity compared to previous implementations of NICE-OHVMS. This work will enable extended high-precision spectroscopic surveys of H3+ and other important molecular ions.

The H 3 + molecular ion has served as a long-standing benchmark for state-of-the-art ab initio calculations of molecular potentials and variational calculations of rovibrational energy levels. However, the accuracy of such calculations would not have been confirmed if not for the wealth of spectroscopic data that has been made available for this molecule. Recently, a new high-precision ion spectroscopy technique was demonstrated by Hodges et al., which led to the first highly accurate and precise (∼MHz) H 3 + transition frequencies. As an extension of this work, we present ten additional R-branch transitions measured to similar precision as a next step toward the ultimate goal of producing a comprehensive high-precision survey of this molecule, from which rovibrational energy levels can be calculated.

Three new rovibrational bands of Ar–D 2 O have been observed in the ν 2 bending region of D 2 O using a quantum cascade laser based cavity ringdown spectrometer. In addition, further observations of the Π(1 10 , ν 2 = 1) ← Σ(1 01 ) band reported by Li et al. (J. Mol. Spectrosc. 272 (2012) 27–31) have been made. All bands were fit by treating the complex using a pseudo-diatomic model which treats the D 2 O as a free rotor within the complex. Molecular constants have been obtained using this model and are reported with deviations in the fits ranging from 0.0002 cm −1 to 0.0005 cm −1 . Two of the newly observed bands are tentatively assigned as the Π(2 02 , ν 2 = 1) ← Σ(1 11 ) and Π(2 11 , ν 2 = 1) ← Σ(2 02 ) bands, which have not previously been observed in other spectral regions.

In diffuse molecular clouds, the nuclear spin temperature of (approx. 30 K) is much lower than the cloud kinetic temperature (approx. 70 K). To understand this temperature discrepancy, we have measured the ratio of the hop to exchange pathways ( α ) in the reaction (which interconverts ortho- and para- ) using high-resolution spectroscopy of the ν 2 fundamental band of in a hydrogenic plasma. We find that α decreases from 1.6±0.1 at 350 K to its statistical value of 0.5±0.1 at 135 K. We use this result to model the steady-state chemistry of diffuse molecular clouds, finding good agreement with astronomical data provided the dissociative recombination rates of ortho- and para- are equal and the identity branching fraction for the reaction is large. Our results highlight the need for further studies of the reaction as well as state-selective measurements of dissociative recombination.

The technique of velocity modulation spectroscopy has recently been combined with cavity enhancement and frequency modulation methods into a technique called noise-immune cavity-enhanced optical heterodyne velocity modulation spectroscopy (NICE-OHVMS). We have implemented NICE-OHVMS with a cw-optical parametric oscillator (OPO) tunable from 3.2 to 3.9 μm, and used it to record spectra of the R(1,0) and R(1,1)u transitions of the ν 2 fundamental band of H 3 + . The high optical power and cavity enhancement enable saturation of rovibrational transitions, which allows for line center frequencies to be measured with a precision of 70 kHz.

We report the rotationally resolved gas phase spectrum of pyrene (C16H10), which is now the largest molecule to be observed with rotational resolution using absorption spectroscopy. This represents a significant advance in the application of absorption spectroscopy to large carbon-containing molecules of fundamental chemical and astronomical importance. Such spectra will facilitate the search for large and highly symmetric molecules in interstellar space, where they may be abundant but cannot be detected without the support of high- resolution laboratory spectra. Detailed assignment and analysis of our spectrum indicates that pyrene is the most rigid rotor yet observed, and that a supersonic expansion cools both the rotational and vibrational temperatures of pyrene vapor produced in an oven source.

Nuclear permutation-inversion (PI) group theory and the linear combination of localized wavefunctions (LCLW) method are applied to the proton “ring-walk” tunneling problem in C6D6H+ and the benzenium ion ( C 6 H 7 + ) . For C6D6H+ and C 6 H 7 + , the rigid and non-rigid MS groups are developed, and their corresponding correlation tables constructed. The reverse correlation relationship is combined with spin statistical restrictions to determine the number of allowed tunneling split levels for both ions. Through the use of the LCLW method and the WKB approximation, the qualitative pattern of the tunneling splitting is presented for C6D6H+. Application of the LCLW problem for the benzenium ion is presented, but the complete treatment to obtain the structure of the tunneling split levels is limited by the computational expense of obtaining the eigenvectors from the diagonalization of the 15 120 × 15 120 connectivity matrix.

We present a follow-up observation on Geballe and Oka (2010, ApJ, 709, L70), who found high column densities of H + � 100 pc apart from the Galactic center on the lines of sight to 2MASS J17432173� 2951430 (J1743) and 2MASS J17470898� 2829561 (J1747). The wavelength coverages on these sightlines have been extended in order to observe two key transitions of H + — R(3, 3) l and R(2, 2) l — which constrain the temperature and density of the environment. The profiles of the H + R(3, 3) l line, which is due only to gas in the Galactic center, closely match the differences between the H + R(1, 1) l and CO line profiles, just as they do for previously studied sightlines in the Galactic center. Absorption in the R(2, 2) l line of H + is present in J1747 at velocities of between � 60 and +100 km s � 1 . This is the second clear detection of this line in the interstellar medium after GC IRS 3 in the Central cluster. The temperature of the absorbing gas in this velocity range is 350 K, significantly warmer than that of diffuse clouds in other parts of the Central Molecular Zone. This indicates that the absorbing gas localizes on the Sgr B molecular cloud complex. The warm and diffuse gas revealed by Oka et al. (2005, ApJ, 632, 882) apparently extends to � 100 pc, but there is a hint that its temperature is somewhat lower in the line of sight to J1743 than elsewhere in the Galactic center. The observation of H + toward J1747 is compared with the recent Herschel observation of H2O +

A continuous wave cavity ringdown spectrometer with a Fabry-Perot quantum cascade laser has been used to collect a rotationally-resolved infrared spectrum of the ν8 vibrational band of methylene bromide in a slit nozzle expansion. In our laboratory, previous observations of the vibrational band were limited by spectral coverage to only the P and Q-branches and by the 24 MHz step-size of the laser [1] . The issue of limited spectral coverage has been resolved using a Fresnel rhomb and a wire grid polarizer to protect the laser from the destabilizing effects of back-reflection from the ringdown cavity. The frequency step-size of the spectrometer has been reduced from 24 MHz to 2 MHz. With both of these instrument enhancements, we have been able to record the R-branch of the vibrational band, and can resolve many lines that were previously blended in spectra acquired using a pinhole expansion nozzle. Significant hyperfine splitting was observed for the low-J transitions in the P and R-branches. It was possible to neglect the effects of hyperfine splitting for transitions involving J″ > 2 in the spectral assignment, and simulations using the constants obtained by fitting to Watson’s S-reduced Hamiltonian for CH279Br81Br, and the A-reduced form for CH279Br2 and CH281Br2, provide a good match to experimental spectra. A total of 297 transitions have been assigned for all three isotopologues, with a standard deviation of 0.00024 cm−1(∼7 MHz).

The new technique of cavity enhanced velocity modulation spectroscopy has been further developed, incorporating a tighter cavity to laser lock and an optical frequency comb for absolute frequency calibration. Several N 2 + transitions have been observed with much higher precision than previously possible, and transitions that were blended in earlier Doppler-limited experiments are now resolved. The full-width at half-maximum of the observed Lamb dips is ∼ 40 MHz , and appears to be dominated by a broadening due to the velocity modulation. Future extension of this technique into the mid-infrared should enable significant improvements in the sensitivity and resolution of vibrational spectroscopy of molecular ions.

In a sample of 114 diffuse cloud sightlines spanning a wide range of interstellar environments, we find the equivalent widths of the diffuse interstellar bands (DIBs) λ6196.0 and λ6613.6 to be extremely well correlated, with a correlation coefficient of 0.986. A maximum likelihood functional relationship analysis shows that the observations are consistent with a perfect correlation if the observational errors, which are dominated by continuum placement and other systematics such as interfering lines, have been underestimated by a factor of 2. The quality of this correlation far exceeds other previously studied correlations, such as that between the λ5780.5 DIB and either the color excess or the atomic hydrogen column density. The unusually tight correlation between these two DIBs would seem to suggest that they might represent the first pair of DIBs known to be due to the same molecular carrier. However, further theoretical work will be required to determine whether the different linewidths and band shapes of these two DIBs can be consistent with a common carrier. If the two DIBs do not in fact share the same molecular carrier, their two carriers must be chemically very closely related.

The reactions of H(3)(+) with CO and with O((3)P) are the two most important reactions for the destruction of H(3)(+) in dense interstellar clouds. These two reactions are studied with sophisticated theoretical methods that should provide accurate predictions for the rate coefficients. The potential energy surfaces are studied with high-level electronic structure methods. For both reactions, simple long-range expansions are shown to be sufficiently accurate for predicting the kinetics at room temperature and lower. The kinetics is predicted from a combination of transition state theory, trajectory simulations, and master equation analysis. For the O((3)P) reaction, the interplay between the spin-orbit and the charge-quadrupole interactions is explicitly considered. For the CO reaction, we also consider the isomerization and decomposition dynamics of the two initially formed adducts. The final predictions, which are expected to be accurate to about 10 to 20%, are compared with the available experimental data. For the O((3)P) reaction, the predicted rate coefficient is accurately reproduced by the expression 1.14 x 10(-9) (T/300)(-0.156) exp(-1.41/T) cm(3) molecule(-1) s(-1) over the 5 to 400 K temperature range. For the CO reaction, the predicted rate coefficients for the H(2) + HCO(+) and H(2) + HOC(+) channels are accurately reproduced by the expressions 1.36 x 10(-9) (T/300)(-0.142) exp(3.41/T) and 8.49 x 10(-10) (T/300)(0.0661) exp(-5.21/T) cm(3) molecule(-1) s(-1), respectively, over the 10 to 400 K temperature range. These revised rate coefficient expressions imply an increase in the destruction of H(3)(+) at temperatures that are typical of dense clouds (10-30 K) by a factor of 2.5 to 3.0.

Although molecular oxygen, O2, has long been thought to be present in interstellar environments, it has only been tentatively detected toward one molecular cloud. The fractional abundance of O2 determined from these observations is well below that predicted by astrochemical models. Given the difficulty of O2 observations from ground-based telescopes, identification of a molecule that could be used as a tracer of O2 in interstellar environments would be quite useful. To this end, we have undertaken a collaborative examination of HO + in an attempt to evaluate the feasibility of its detection in interstellar clouds. We have conducted high-level ab initio calculations of its structure to obtain its molecular parameters. The reaction responsible for the formation of HO + is nearly thermoneutral, and so a careful analysis of its thermochemistry was also required. Using the Active Thermochemical Tables approach, we have determined the most accurate values available to date for the proton affinities of O2 and H2, and the enthalpy, Gibbs energy, and equilibrium constant for the reaction H + +O 2 → HO + +H 2. We find that while this reaction is endothermic by 50 ± 9c m −1 at 0 K, its equilibrium is shifted toward HO + at the higher temperatures of hot cores. We have examined the potential formation and destruction pathways for HO + in interstellar environments. Combining this information, we estimate the HO + column density in dense clouds to be ∼10 9 cm −2 , which corresponds to line brightness temperatures of0.2 mK. If our results prove correct, HO + is clearly not a detectable interstellar molecule.

Major progress has been made in the understanding of how H 3 + recombines with thermal and sub-thermal electrons, a process of great importance to the chemistry of diffuse interstellar clouds. Two independent ion storage ring experiments with rovibrationally cold H 3 + ions are in excellent agreement, and quantum mechanical calculations agree with the storage ring results quantitatively for the thermal rate constant, if not in all details concerning the cross section. The recombination mechanism is understood. A direct consequence of this progress is that the cosmic-ray ionization rate in diffuse clouds must be shifted upwards to a value larger than 10 −16 s −1 .

The A 2 Π u – X 2 Σ g + system of N 2 + was first observed in auroral emissions by Meinel in 1950. Although the N 2 + band system has been reinvestigated since this first spectral study, no laboratory spectrum of the (2, 1) vibronic band has been obtained. We have recently built a continuous-wave cavity ringdown spectrometer, and as a first test of this spectrometer we observed the (2, 1) band of N 2 + in a positive column discharge cell. Many lines of the first positive band system of N 2 ∗ were also identified during the process of assigning this spectrum. The relative intensities of the N 2 ∗ and N 2 + bands were found to change with discharge cell pressure, and so each spectral region was observed at two pressures to aid in distinguishing the spectra of the two species. We have assigned 125 N 2 + lines and determined the molecular parameters for the (2, 1) band from these assignments. The analysis of the N 2 ∗ spectrum is ongoing and will be presented in a follow-up paper. The N 2 + (2, 1) band transition frequencies predicted from available literature values vary significantly from our assignments. The observed deviations indicate correlation of other parameters with the spin-rotation parameter and the quartic centrifugal distortion constants. These results indicate that rovibronic predictions for new N 2 + bands based on the parameters derived from individual band assignments are likely to be unreliable, and further investigation of the Meinel system may require a global analysis that accounts for this correlation.

Using high resolution infrared spectroscopy we have surveyed twenty sightlines for H3+ absorption. H3+ is detected in eight diffuse cloud sightlines with column densities varying from 0.6x10^14 cm^-2 to 3.9x10^14 cm^-2. This brings to fourteen the total number of diffuse cloud sightlines where H3+ has been detected. These detections are mostly along sightlines concentrated in the Galactic plane, but well dispersed in Galactic longitude. The results imply that abundant H3+ is common in the diffuse interstellar medium. Because of the simple chemistry associated with H3+ production and destruction, these column density measurements can be used in concert with various other data to infer the primary cosmic-ray ionization rate, zeta_p. Values range from 0.5x10^-16 s^-1 to 3x10^-16 s^-1 with an average of 2x10^-16 s^-1. Where H3+ is not detected the upper limits on the ionization rate are consistent with this range. The average value of zeta_p is about an order of magnitude larger than both the canonical rate and rates previously reported by other groups using measurements of OH and HD. The discrepancy is most likely due to inaccurate measurements of rate constants and the omission of effects which were unknown when those studies were performed. We believe that the observed column density of H3+ is the most direct tracer for the cosmic-ray ionization rate due to its simple chemistry. Recent models of diffuse cloud chemistry require cosmic-ray ionization rates on the order of 10^-16 s^-1 to reproduce observed abundances of various atomic and molecular species, in rough accord with our observational findings.

Polycyclic aromatic hydrocarbons (PAHs) have been proposed as potential carriers of the unidentified infrared bands (UIRs) and the diffuse interstellar bands (DIBs). PAHs are not likely to form by gas-phase or solid-state interstellar chemistry, but rather might be produced in the outflows of carbon-rich evolved stars. PAHs could form from acetylene addition to the phenyl radical (C6H5), which is closely chemically related to benzene (C6H6) and ortho-benzyne (o-C6H4). To date, circumstellar chemical models have been limited to only a partial treatment of benzene-related chemistry, and so the expected abundances of these species are unclear. A detection of benzene has been reported in the envelope of the proto-planetary nebula (PPN) CRL 618, but no other benzene-related species has been detected in this or any other source. The spectrum of o-C6H4 is significantly simpler and stronger than that of C6H5, and so we conducted deep Ku-, K- and Q-band searches for o-C6H4 with the Green Bank Telescope. No transitions were detected, but an upper limit on the column density of 8.4x10^13 cm^-2 has been determined. This limit can be used to constrain chemical models of PPNe, and this study illustrates the need for complete revision of these models to include the full set of benzene-related chemistry., Comment: 13 pages, 4 figures, to be published in The Astrophysical Journal Letters

plays a key role in interstellar chemistry as the initiator of ion–molecule chemistry. The amount of observed in dense interstellar clouds is consistent with expectations, but the large abundance of seen in diffuse clouds is not easily explained by simple chemical models. A crucial parameter in predicting the abundance of in diffuse clouds is the rate constant for dissociative recombination (DR) with electrons. The value of this constant has been very controversial, because different experimental techniques have yielded very different results, perhaps owing to varying degrees of rotational and vibrational excitation of the ions. If the value of this rate constant under interstellar conditions were much lower than usually assumed, the large abundance could be easily explained. In an attempt to pin down this crucial rate constant, we have performed DR measurements at the CRYRING ion storage ring in Stockholm, using a supersonic expansion ion source to produce rotationally cold ions. These measurements suggest that the DR rate constant in diffuse clouds is not much lower than usually assumed and that the abundant must be due to either a low electron fraction or a high ionization rate.

Diffuse interstellar clouds have long been thought to be relatively devoid of molecules, because of their low densities and high radiation fields. However, in the past ten years or so, a plethora of polyatomic molecules have been observed in diffuse clouds, via their rotational, vibrational, and electronic transitions. In this review, we propose a new systematic classification method for the different types of interstellar clouds: diffuse atomic, diffuse molecular, translucent, and dense. We review the observations of molecules (both diatomic and polyatomic) in diffuse clouds and discuss how molecules can be utilized as indicators of the physical and chemical conditions within these clouds. We review the progress made in the modeling of the chemistry in these clouds, and the (significant) challenges that remain in this endeavor. We also review the evidence for the existence of very large molecules in diffuse clouds, and discuss a few specific clouds of particular interest.

We confirm the first detection of the molecular ion H3+ in an extragalactic object, the highly obscured ultraluminous galaxy IRAS 08572+3915 NW. We also have detected absorption lines of the fundamental band of CO in this galaxy. The CO absorption consists of a cold component close to the systemic velocity and warm, highly blueshifted and redshifted components. The warm blueshifted component is remarkably strong and broad and extends at least to -350 km/s. Some analogies can be drawn between the H3+ and cold CO in IRAS08572+3915 NW and the same species seen toward the Galactic center. The profiles of the warm CO components are not those expected from a dusty torus of the type thought to obscure active galactic nuclei. They are probably formed close to the dust continuum surface near the buried and active nucleus and are probably associated with an unusual and energetic event there.