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We present broadband dual frequency comb laser absorption measurements of 2% H$_2$O (natural isotopic abundance of 99.7% H$_2^{16}$O) in air from 6600-7650 cm$^{-1}$ (1307-1515 nm) with a spectral point spacing of 0.0068 cm$^{-1}$. Twenty-nine datasets were collected at temperatures between 300 and 1300 K ($\pm$0.82% average uncertainty) and pressures ranging from 20 to 600 Torr ($\pm$0.25%) with an average residual absorbance noise of 8.0E-4 across the spectrum for all measurements. We fit measurements using a quadratic speed-dependent Voigt profile to determine 7088 absorption parameters for 3366 individual transitions found in HITRAN2020. These measurements build on the line strength, line center, self-broadening, and self-shift parameters determined in the Part I companion of this work. Here we measure air-broadened width (with temperature- and speed-dependence) and air pressure shift (with temperature dependence) parameters. Various trends are explored for extrapolation to weak transitions that were not covered in this work. Improvements made in this work are predominantly due to the inclusion of air pressure shift temperature dependence values. In aggregate, these updates improved RMS absorbance error by a factor of 4.2 on average, and the remaining residual is predominantly spectral noise. This updated database improves high temperature spectroscopic knowledge across the 6600 7650 cm$^{-1}$ region of H$_2$O absorption., Comment: Database files available upon request. Will be included with published manuscript following review process

New and existing rotational spectra of methyl cyanide were analyzed to extend the global model of low-lying vibrational states and their interactions to $v_4=1$ at 920 cm$^{-1}$. The rotational spectra cover large portions of the 36$-$1439 GHz region and reach quantum numbers $J$ and $K$ of 79 and 16, respectively. Information on the $K$ level structure of CH$_3$CN is obtained from IR spectra. A spectrum of $2\nu_8$ around 717 cm$^{-1}$, analyzed in our previous study, covered also the $\nu_4$ band. The assignments in this band cover 880$-$952 cm$^{-1}$, attaining quantum numbers $J$ and $K$ of 61 and 13, respectively. The most important interaction of $v_4=1$ appears to be with $v_8=3$, $\Delta K=0$, $\Delta l=+3$, a previously characterized anharmonic resonance. We report new analyses of interactions with $\Delta K=-2$ and $\Delta l=+1$, with $\Delta K=-4$ and $\Delta l=-1$, and with $\Delta K=-6$ and $\Delta l=-3$; these four types of interactions connect all $l$ substates of $v_8=3$ in energy to $v_4=1$. A known $\Delta K=-2$, $\Delta l=+1$ interaction with $v_7=1$ was also analyzed, and investigations of the $\Delta K=+1$, $\Delta l=-2$ and $\Delta K=+3$, $\Delta l=0$ resonances with $v_8=2$ were improved, as were interactions between successive states with $v_8\le 3$, mainly through new $v_8\le 2$ rotational data. A preliminary single state analysis of the $v_4=v_8=1$ state was carried out based on rotational transition frequencies and on $\nu_4+\nu_8-\nu_8$ hot band data. A considerable fraction of the $K$ levels was reproduced within uncertainties in its entirety or in part, despite obvious widespread perturbations in $v_4=v_8=1$. We detect rotational transitions of methyl cyanide from within all vibrational states up to $v_4=1$ and $v_4=v_8=1$ tentatively toward the hot molecular core of Sagittarius B2(N) employing the Atacama Large Millimeter Array., Comment: 30 pages, J. Mol. Spectrosc., accepted

The chloroniumyl cation, HCl$^+$, has been recently identified in space from Herschel's spectra. A joint analysis of extensive vis-UV spectroscopy emission data together with a few high resolution and high accuracy mm-wave data provided the necessary rest frequencies to support the astronomical identification. Nevertheless, the analysis did not include any infrared vibration-rotation data. Furthermore, with the end of the Herschel mission, infrared observations from ground may be one of the few available means to further study this ion in space. In this work we provide a set of accurate rovibrational transition wavenumbers as well as a new and improved global fit of vis-UV, IR and mm-wave spectroscopy laboratory data, that will aid in future studies of this molecule., Comment: Published in the Astrophysical Journal Letters

Spectra of methyl cyanide were recorded to analyze interactions in low-lying vibrational states and to construct line lists for radio astronomical observations as well as for infrared spectroscopic investigations of planetary atmospheres. The rotational spectra cover large portions of the 36$-$1627 GHz region. In the infrared (IR), a spectrum was recorded for this study in the region of 2$\nu _8$ around 717 cm$^{-1}$ with assignments covering 684$-$765 cm$^{-1}$. Additional spectra in the $\nu _8$ region were used to validate the analysis. The large amount and the high accuracy of the rotational data extend to much higher $J$ and $K$ quantum numbers and allowed us to investigate for the first time in depth local interactions between these states which occur at high $K$ values. In particular, we have detected several interactions between $v_8 = 1$ and 2. Notably, there is a strong $\Delta v_8 = \pm1$, $\Delta K = 0$, $\Delta l = \pm3$ Fermi resonance between $v_8 = 1^{-1}$ and $v_8 = 2^{+2}$ at $K$ = 14. Pronounced effects in the spectrum are also caused by resonant $\Delta v_8 = \pm1$, $\Delta K = \mp2$, $\Delta l = \pm1$ interactions between $v_8 = 1$ and 2. An equivalent resonant interaction occurs between $K$ = 14 of the ground vibrational state and $K$ = 12, $l = +1$ of $v_8 = 1$ for which we present the first detailed account. A preliminary account was given in an earlier study on the ground vibrational state. From data pertaining to $v_8 = 2$, we also investigated rotational interactions with $v_4 = 1$ as well as $\Delta v_8 = \pm1$, $\Delta K = 0$, $\Delta l = \pm3$ Fermi interactions between $v_8 = 2$ and 3. We have derived N$_2$- and self-broadening coefficients for the $\nu _8$, 2$\nu _8 - \nu _8$, and 2$\nu _8$ bands from previously determined nu4 values. Subsequently, we determined transition moments and intensities for the three IR bands., Comment: 20 pages, astract abbreviated; appeared in Journal of Molecular Spectroscopy; CDMS links updated; dipole values in Table 10 corrected (were correct in text)

The Polar Radiant Energy in the Far-Infrared Experiment (PREFIRE) is a low-cost cubesat-based Earth Science mission selected for rapid implementation through NASAs Earth Ventures-Instrument program. Two cubesats carrying thermal infrared spectrometers (TIRS) in polar orbits will test long-held assumptions regarding radiative balance at long wavelengths where the cold-dry Arctic and Antarctic surfaces expel significant amounts of the earth's radiant energy. Thermal radiometry with better than one micron sampling at wavelengths beyond 15 microns will provide critical observational bounds for inputs into glacier melt and climate change models through improvements in surface emissivities, longwave greenhouse effect parameterizations, and cloud presence/types. Additional information on potential far-infrared surface/atmosphere feedbacks during rapid melt processes may be captured with sub-diurnal revisits of targeted areas. A baseline mission with two cubesats in different orbits provides a means for optimization of sub-diurnal sampling for science purposes. In this presentation we provide details of orbit studies that inform expected sampling metrics. Candidate orbits are modeled in SGP and then TIRS sampling is projected into surface footprints with appropriate geo-location. Matching algorithms then compile statistics for time-delayed revisits between and within the two orbits. Binning of results by latitude allows for abstraction of precession issues as well as for correlations with surface types as defined by radiometric classification schemes. Multiple acceptable pairs of science-driven orbits were found that optimize sampling in areas known to experience rapid melt events. The final choice of PREFIRE orbital parameters includes the systems trade-space, particularly the power budget, as well as the availability of launch opportunities.

Methyl cyanide is an important trace molecule in star-forming regions. It is one of the more common molecules used to derive kinetic temperatures in such sources. As preparatory work for Herschel, SOFIA, and in particular ALMA we want to improve the rest frequencies of the main as well as minor isotopologs of methyl cyanide. The laboratory rotational spectrum of methyl cyanide in natural isotopic composition has been recorded up to 1.63 THz. Transitions with good signal-to-noise ratio could be identified for CH$_3$CN, $^{13}$CH$_3$CN, CH$_3^{13}$CN, CH$_3$C$^{15}$N, CH$_2$DCN, and $^{13}$CH$_3^{13}$CN in their ground vibrational states up to about 1.2 THz. The main isotopic species could be identified even in the highest frequency spectral recordings around 1.6 THz. The highest $J'$ quantum numbers included in the fit are 64 for $^{13}$CH$_3^{13}$CN and 89 for the main isotopic species. Greatly improved spectroscopic parameters have been obtained by fitting the present data together with previously reported transition frequencies. The present data will be helpful to identify isotopologs of methyl cyanide in the higher frequency bands of instruments such as the recently launched Herschel satellite, the upcoming airplane mission SOFIA or the radio telescope array ALMA., Comment: 13 pages, 2 figures, article appeared; CDMS links updated

We have measured new submillimeter-wave data around 600 GHz and around 1.1 THz for the 13C isotopologue of formic acid and for the two deuterium isotopomers; in each case for both the trans and cis rotamer. For cis-DCOOH and cis-HCOOD in particular only data up to 50 GHz was previously available. For all species the quality and quantity of molecular parameters has been increased providing new measured frequencies and more precise and reliable frequencies in the range of existing and near-future submillimeter and far-infrared astronomical spectroscopy instruments such as Herschel, SOFIA and ALMA.

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