Muonic hydrogen cascade time and lifetime of the short-lived 2S2S state

Metastable ${2S}$ muonic-hydrogen atoms undergo collisional ${2S}$-quenching, with rates which depend strongly on whether the $\mu p$ kinetic energy is above or below the ${2S}\to {2P}$ energy threshold. Above threshold, collisional ${2S} \to {2P}$ excitation followed by fast radiative ${2P} \to {1S}$ deexcitation is allowed. The corresponding short-lived $\mu p ({2S})$ component was measured at 0.6 hPa $\mathrm{H}_2$ room temperature gas pressure, with lifetime $\tau_{2S}^\mathrm{short} = 165 ^{+38}_{-29}$ ns (i.e., $\lambda_{2S}^\mathrm{quench} = 7.9 ^{+1.8}_{-1.6} \times 10^{12} \mathrm{s}^{-1}$ at liquid-hydrogen density) and population $\epsilon_{2S}^\mathrm{short} = 1.70^{+0.80}_{-0.56}$ % (per $\mu p$ atom). In addition, a value of the $\mu p$ cascade time, $T_\mathrm{cas}^{\mu p} = (37\pm5)$ ns, was found.Comment: 4 pages, 3 figure

O-H...O, C-H...O and C-H...[pi]arene intermolecular interactions in (2S)-2-(1-oxo-1H-2,3-dihydroisoindol-2-yl)pentanoic acid and (2S)-3-methyl-2-(1-oxo-1H-2,3-dihydroisoindol-2-yl)butanoic acid

In the first of the title compounds, (2S)-2-(1-oxo-1H-2,3-dihydroisoindol-2-yl)pentanoic acid, C₁₃H₁₅NO₃, prepared from L-norvaline, a hydrogen-bonded network is formed in the solid state through O-H...O=C, C-H...O=C and C-H...πarene intermolecular interactions, with shortest O...O, C...O and C...centroid distances of 2.582 (13), 3.231 (11) and 3.466 (3) Å, respectively. In the L-valine derivative, (2S)-3-methyl-2-(1-oxo-1H-2,3-dihydroisoindol-2-yl)butanoic acid, C₁₃H₁₅NO₃, O-H...O=C and Carene-H...O=C intermolecular interactions generate a cyclic R²₂(9) motif through cooperativity, with shortest O...O and C...O distances of 2.634 (3) and 3.529 (5) Å, respectively. Methylene C-H...O=Cindole interactions complete the hydrogen bonding, with C...O distances ranging from 3.283 (4) to 3.477 (4) Å

Intermolecular interactions in the chiral and racemic forms of 3-hydroxy-2-(1-oxoisoindolin-2-yl)butanoic acid derived from threonine

The title compounds, C₁₂H₁₃NO₄, are derived from L-threonine and DL-threonine, respectively. Hydrogen bonding in the chiral derivative, (2S/3R)-3-hydroxy-2-(1-oxoisoindolin-2-yl)butanoic acid, consists of O-Hacid...Oalkyl-H...O=Cindole chains [O...O 2.659 (3) and 2.718 (3) Å], Csp³-H...O and three C-H...πarene interactions. In the (2R,3S/2S,3R) racemate, conventional carboxylic acid hydrogen bonding as cyclical (O-H...O=C)₂ [graph set R₂²(8)] is present, with Oalkyl-H...O=Cindole, Csp³-H...O and C-H...πarene interactions. The COOH group geometry differs between the two forms, with C-O, C=O, C-C-O and C-C=O bond lengths and angles of 1.322 (3) and 1.193 (3) Å, and 109.7 (2) and 125.4 (3)°, respectively, in the chiral structure, and 1.2961 (17) and 1.2210 (18) Å, and 113.29 (12) and 122.63 (13)°, respectively, in the racemate structure. The O-C=O angles of 124.9 (3) and 124.05 (14)° are similar. The differences arise from the contrasting COOH hydrogen-bonding environments in the two structures