Direct Spectroscopic detection of the orientation of free OH groups in methyl lactate-(water)(1,2) clusters: hydration of a chiral hydroxy ester.

Hydration of chiral molecules is a subject of significant current interest in light of recent experimental observations of chirality transfer from chiral solutes to water in solution and the important roles which water plays in biological events. Using a broadband chirped pulse and a cavity based microwave spectrometer, we detected spectroscopic signatures of the mono- and dihydrates of methyl lactate, a chiral hydroxy ester. Surprisingly, these small hydration clusters show highly specific binding preferences.

Rotational spectroscopic study of hydrogen cyanide embedded in small 4He clusters.

High resolution microwave spectra of the a-type, J = 1-0, transitions of He(N = 1-6)-H(12)C(14)N, He(N = 1-6)-H(13)C(14)N, He(N = 1-6)-H(12)C(15)N, He(N = 1-7)-D(12)C(14)N, and He(N = 1-6)-D(13)C(14)N clusters produced in a supersonic jet expansion were measured and analyzed. The resulting effective rotational constants, B(eff), initially decrease with the number of the attached helium atoms before reaching a minimum at N = 3 helium atoms for all isotopologues. The subsequent increase in B(eff) for N ≥ 4 is indicative of the onset of microscopic superfluidity.

Kinetics of the reaction of the heaviest hydrogen atom with H2, the 4Heμ + H2 → 4HeμH + H reaction: experiments, accurate quantal calculations, and variational transition state theory, including kinetic isotope effects for a factor of 36.1 in isotopic mass.

The neutral muonic helium atom (4)Heμ, in which one of the electrons of He is replaced by a negative muon, may be effectively regarded as the heaviest isotope of the hydrogen atom, with a mass of 4.115 amu. We report details of the first muon spin rotation (μSR) measurements of the chemical reaction rate constant of (4)Heμ with molecular hydrogen, (4)Heμ + H(2) → (4)HeμH + H, at temperatures of 295.

Kinetic isotope effects for the reactions of muonic helium and muonium with H2.

The neutral muonic helium atom may be regarded as the heaviest isotope of the hydrogen atom, with a mass of ~4.1 atomic mass units ((4.1)H), because the negative muon almost perfectly screens one proton charge.

Pulsed quantum cascade laser-based cavity ring-down spectroscopy for ammonia detection in breath.

Breath analysis can be a valuable, noninvasive tool for the clinical diagnosis of a number of pathological conditions. The detection of ammonia in exhaled breath is of particular interest for it has been linked to kidney malfunction and peptic ulcers. Pulsed cavity ringdown spectroscopy in the mid-IR region has developed into a sensitive analytical technique for trace gas analysis.

Ultraviolet spectroscopy of pyrene in a supersonic jet and in liquid helium droplets.

In a series of experiments devoted to the study of polycyclic aromatic hydrocarbons for astrophysical applications, the S(2)<--S(0) transition of jet-cooled pyrene (C(16)H(10)) at 321 nm has been studied by an absorption technique for the first time. The spectra observed by cavity ring-down spectroscopy closely resemble the excitation spectra obtained earlier by laser-induced fluorescence (LIF) and show the same band clusters arising from the vibronic interaction of S(2) with S(1). We have also investigated pyrene when it was incorporated into 380 mK cold helium droplets.