Infrared spectra of C2H2 under jet-cooled and para-H2 matrix conditions

Matrix Isolation Spectroscopy and Nuclear Spin Conversion of Propyne Suspended in Solid Parahydrogen

Parahydrogen (pH₂) quantum solids are excellent matrix isolation hosts for studying the rovibrational dynamics and nuclear spin conversion (NSC) kinetics of molecules containing indistinguishable nuclei with nonzero spin. The relatively slow NSC kinetics of propyne (CH₃CCH) isolated in solid pH₂ is employed as a tool to assign the rovibrational spectrum of propyne in the 600-7000 cm^-1 region. Detailed analyses of a variety of parallel (ΔK = 0) and perpendicular (ΔK=±1) bands of propyne indicate that the end-over-end rotation of propyne is quenched, but K rotation of the methyl group around the C₃ symmetry axis still persists. However, this single-axis K rotation is significantly hindered for propyne trapped in solid pH₂ such that the energies of the K rotational states do not obey simple energy-level expressions. The NSC kinetics of propyne follows first-order reversible kinetics with a 287(7) min effective time constant at 1.7 K. Intensity-intensity correlation plots are used to determine the relative line strengths of individual ortho- and para-propyne rovibrational transitions, enabling an independent estimation of the ground vibrational state effective A″ constant of propyne.

Molecular structures of gas-phase neutral morpholine and its monohydrated complexes: experimental and theoretical approaches

Morpholine (NH(CH₂CH₂)₂O) is a typical six-membered aliphatic heterocyclic compound.

Multiplet splittings and intensities of fine structure components of the Q1(0)H2 + S0(0)N2 transition in a solid parahydrogen matrix

A comprehensive analysis of theoretical multiplet splittings and intensities of the fine structure components of the Q(1)(0)H(2) + S(0)(0)N(2) transition in a solid parahydrogen crystal is presented. The consideration of higher order anisotropic term responsible for splittings is essential to explain the observed splitting of the three components. The pair interaction parameters DeltaB and DeltaC have been determined by comparing the theoretical splittings with the experimental values. The information about the small splittings (approximately 0.1 cm(-1)) due to crystal-field interaction is completely obscured due to fast hopping of v(') = 1, J(') = 0 H(2) vibron. Also, the theoretical expressions are derived for the intensities of the fine structure components of the Q(v(H(2)))(0) + S(v(N(2)))(0) transition and the theoretical results are compared with the experimental findings.