Direct observation of superfluid response in para-hydrogen (p-H(2)) remains a challenge because of the need for a probe that would not induce localization and a resultant reduction in superfluid ...fraction. Earlier work H. Li, R. J. Le Roy, P.-N. Roy, and A. R. W. McKellar, Phys. Rev. Lett. 105, 133401 (2010) has shown that carbon dioxide can probe the effective inertia of p-H(2) although larger clusters show a lower superfluid response due to localization. It is shown here that the lighter carbon monoxide probe molecule allows one to measure the effective inertia of p-H(2) clusters while maintaining a maximum superfluid response with respect to dopant rotation. Microwave spectroscopy and a theoretical analysis based on Feynman path-integral simulations are used to support this conclusion.
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•The HITRAN2020 molecular spectroscopic database and its validations are presented.•Extended line-by-line coverage to 55 molecules, with new isotopologues included.•Increased spectral and dynamic ...ranges for multiple molecules.•Quality and amount of spectral parameters (including sophisticated line shapes) is increased.•Updates to cross sections, CIA, software tools & auxiliary data also described.
The HITRAN database is a compilation of molecular spectroscopic parameters. It was established in the early 1970s and is used by various computer codes to predict and simulate the transmission and emission of light in gaseous media (with an emphasis on terrestrial and planetary atmospheres). The HITRAN compilation is composed of five major components: the line-by-line spectroscopic parameters required for high-resolution radiative-transfer codes, experimental infrared absorption cross-sections (for molecules where it is not yet feasible for representation in a line-by-line form), collision-induced absorption data, aerosol indices of refraction, and general tables (including partition sums) that apply globally to the data. This paper describes the contents of the 2020 quadrennial edition of HITRAN. The HITRAN2020 edition takes advantage of recent experimental and theoretical data that were meticulously validated, in particular, against laboratory and atmospheric spectra. The new edition replaces the previous HITRAN edition of 2016 (including its updates during the intervening years).
All five components of HITRAN have undergone major updates. In particular, the extent of the updates in the HITRAN2020 edition range from updating a few lines of specific molecules to complete replacements of the lists, and also the introduction of additional isotopologues and new (to HITRAN) molecules: SO, CH3F, GeH4, CS2, CH3I and NF3. Many new vibrational bands were added, extending the spectral coverage and completeness of the line lists. Also, the accuracy of the parameters for major atmospheric absorbers has been increased substantially, often featuring sub-percent uncertainties. Broadening parameters associated with the ambient pressure of water vapor were introduced to HITRAN for the first time and are now available for several molecules.
The HITRAN2020 edition continues to take advantage of the relational structure and efficient interface available at www.hitran.org and the HITRAN Application Programming Interface (HAPI). The functionality of both tools has been extended for the new edition.
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High resolution microwave and millimeter-wave spectra of HeN-CO clusters with N up to 10, produced in a molecular expansion, were observed. Two series of J = 1-0 transitions were detected, which ...correspond to the a-type and b-type J = 1-0 transitions of He1-CO. The B rotational constant initially decreases with N and reaches a minimum at N = 3. Its subsequent rise indicates the transition from a molecular complex to a quantum solvated system already for N = 4. For N > or =6, the B value becomes larger than that of He1-CO, indicating an almost free rotation of CO within the helium environment.
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The rotational spectrum of the CO-para-H2 van der Waals complex, produced using a molecular jet expansion, was observed with two different techniques: OROTRON intracavity millimeter-wave spectroscopy ...and pulsed Fourier transform microwave spectroscopy. Thirteen transitions in the frequency range from 80 to 130 GHz and two transitions in the 14 GHz region were measured and assigned, allowing for a precise determination of the corresponding energy level positions of CO-para-H2. The data obtained enable further radio astronomical searches for this molecular complex and provide a sensitive test of the currently best available intermolecular potential energy surface for the CO-H2 system.
High resolution microwave (a-type) and millimetre-wave (b-type) spectra of He(N)-(13)C(16)O, He(N)-(12)C(18)O, and He(N)-(13)C(18)O clusters (N<or= 10) were observed, significantly extending the ...initial spectroscopic observations on He(N)-(12)C(16)O by Surin et al. Phys. Rev. Lett., 2008, 101, 233401. The frequencies of the a-type series, which evolves from the end-over-end rotation of the dimer, decrease from N = 1 to 3, then increase smoothly to at least N = 9. This turnaround indicates a rapid evolution of the solvation character from classical to quantum. The b-type series, which evolves from the free molecule rotation of CO, increases from N = 0 to 6 and then decreases to at least N = 10. This is consistent with an initially increasing anisotropy of the helium environment, followed by a tendency of the solvation shell to become more isotropic. The shift of the vibrational frequency of CO as determined from the infrared A. R. W. McKellar, J. Chem. Phys., 2004, 121, 6868; ibid., 2006, 125, 164328 and microwave data reveals an approximately linear decrease from N = 1 to at least 9. If the linear shift were to continue until completion of the first solvation shell (N approximately 14), the estimated helium nanodroplet shift will be well undershot K. von Haeften, S. Rudolph, I. Simanovski, M. Havenith, R. E. Zillich and K. B. Whaley, Phys. Rev. B: Condens. Matter Mater. Phys., 2006, 73, 054502. In this case, there must be an upturn in the vibrational shift beyond N = 14, which is not predicted by theory T. Skrbić, S. Moroni and S. Baroni, J. Phys. Chem. A, 2007, 111, 7640. By extrapolating the a-type series to N = 14 (assuming a linear vibrational shift), we estimate the rotational constant, B, of CO in the helium nanodroplet to be approximately 74% of its gas phase value. This is in reasonable agreement with simulations (76% at N = 14), which predict the limiting value to be approximately reached upon completion of the first solvation shell (73% at N = 100) T. Skrbić, S. Moroni and S. Baroni, J. Phys. Chem. A, 2007, 111, 7640. However, this value is significantly larger than that inferred from helium nanodroplet experiments (63%).
Understanding Solid/Solid Organic Reactions Rothenberg, Gadi; Downie, Andrew P; Raston, Colin L ...
Journal of the American Chemical Society,
09/2001, Volume:
123, Issue:
36
Journal Article
Peer reviewed
The concept of an organic reaction between two macroscopic solid particles is investigated. Thus, we study several reactions that have been recently reported to proceed “in the solid phase” and ...clearly show that, in most cases, grinding the two solid reactants together results in the formation of a liquid phase. This is true both for catalytic transformations (e.g., aldol condensations and oligomerization of benzylic compounds) and for noncatalytic reactions (Baeyer−Villiger oxidations, oxidative coupling of naphthols using iron chloride, condensation of amines and aldehydes to form azomethines, homo-etherification of benzylic alcohols using p-toluenesulfonic acid, and nuclear aromatic bromination with NBS). This liquefaction implies the existence of a eutectic mixture with T fusion below ambient temperature (although both reagents have higher than ambient melting points). In cases where heating is required, it is again clear that a phase change (from solid to liquid) occurs, explaining the observed reaction kinetics. On the basis of 19 experimental examples, we discuss the possibility of solid-phase organic reactions and the implications of these findings to the reaction between two solid reagents. A general description of such reactive systems is proposed, based on a consideration of the potential for eutectic (or peritectic) formation between the constituents of the liquid phases that arise during the process of mechanical mixing of the solid reagents and products.
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High resolution microwave (
a
-type) and millimetre-wave (
b
-type) spectra of He
N
-
13
C
16
O, He
N
-
12
C
18
O, and He
N
-
13
C
18
O clusters (
N
≤ 10) were observed, significantly extending the ...initial spectroscopic observations on He
N
-
12
C
16
O by Surin
et al.
Phys. Rev. Lett.
, 2008,
101
, 233401. The frequencies of the
a
-type series, which evolves from the
end
-
over
-
end
rotation of the dimer, decrease from
N
= 1 to 3, then increase smoothly to at least
N
= 9. This turnaround indicates a rapid evolution of the solvation character from classical to quantum. The
b
-type series, which evolves from the
free molecule
rotation of CO, increases from
N
= 0 to 6 and then decreases to at least
N
= 10. This is consistent with an initially increasing anisotropy of the helium environment, followed by a tendency of the solvation shell to become more isotropic. The shift of the vibrational frequency of CO as determined from the infrared A. R. W. McKellar,
J. Chem. Phys.
, 2004,
121
, 6868;
ibid.
, 2006,
125
, 164328 and microwave data reveals an approximately linear decrease from
N
= 1 to at least 9. If the linear shift were to continue until completion of the first solvation shell (
N
14), the estimated helium nanodroplet shift will be well undershot K. von Haeften, S. Rudolph, I. Simanovski, M. Havenith, R. E. Zillich and K. B. Whaley,
Phys. Rev. B: Condens. Matter Mater. Phys.
, 2006,
73
, 054502. In this case, there must be an upturn in the vibrational shift beyond
N
= 14, which is not predicted by theory T. Škrbi , S. Moroni and S. Baroni,
J. Phys. Chem. A
, 2007,
111
, 7640. By extrapolating the
a
-type series to
N
= 14 (assuming a linear vibrational shift), we estimate the rotational constant,
B
, of CO in the helium nanodroplet to be ∼74% of its gas phase value. This is in reasonable agreement with simulations (76% at
N
= 14), which predict the limiting value to be approximately reached upon completion of the first solvation shell (73% at
N
= 100) T. Škrbi , S. Moroni and S. Baroni,
J. Phys. Chem. A
, 2007,
111
, 7640. However, this value is significantly larger than that inferred from helium nanodroplet experiments (63%).
Isotopic studies of helium
N
-carbon monoxide clusters shed light on the evolution of microscopic superfluidity.
Nature applies enzymatic assembly lines to synthesize bioactive compounds. Inspired by such capabilities, we have developed a facile method for spatially segregating attached enzymes in a ...continuous‐flow, vortex fluidic device (VFD). Fused Hisn‐tags at the protein termini allow rapid bioconjugation and consequent purification through complexation with immobilized metal affinity chromatography (IMAC) resin. Six proteins were purified from complex cell lysates to average homogeneities of 76 %. The most challenging to purify, tobacco epi‐aristolochene synthase, was purified in only ten minutes from cell lysate to near homogeneity (>90 %). Furthermore, this “reaction‐ready” system demonstrated excellent stability during five days of continuous‐flow processing. Towards multi‐step transformations in continuous flow, proteins were arrayed as ordered zones on the reactor surface allowing segregation of catalysts. Ordering enzymes into zones opens up new opportunities for continuous‐flow biosynthesis.
Multi‐step biocatalysis goes with the flow: Several enzymes were immobilized into distinct, ordered zones in a thin film continuous‐flow reactor. Telescoping protein immobilization and purification creates a “reactor‐ready” system in ten minutes from cell lysates. This advancement is poised to facilitate on‐demand synthesis of compounds using enzymatic pathways.
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