No abstract

5-7 mm in length were used. The pressure was measured using the pressure dependence of the superconducting transition temperature of a built-in pressure sensor made of high-purity tin [23]. Experimental data were corrected for diamagnetism using Pascal's constants.Visible Absorption Spectroscopy under Hydrostatic Pressure: Full absorption spectra were recorded between 450 and 750 nm by using a Carl Zeiss PGS-2 spectrometer. The hydrostatic-pressure cell made of hardened beryllium bronze with NaCl as the pressure-transmitting medium operated in the pressure range 10 5 Pa < P < 3 GPa (accuracy ≈ ± 0.1 GPa). The pressure was measured using the pressure dependence of ruby [24].

Abstract. The heterogeneous uptake of methylamine (MA) onto (NH 4 ) 2 SO 4 , NH 4 HSO 4 , NH 4 NO 3 and NH 4 Cl was investigated using a Knudsen cell reactor coupled to a quadrupole mass spectrometer, in situ Raman spectrometer and theoretical calculations. Exchange reactions were observed between MA and NH 4 NO 3 , (NH 4 ) 2 SO 4 , and NH 4 Cl were observed at 298 K. Simple acid-base reaction for MA was found taking place on NH 4 HSO 4 . CH 3 NH 3 NO 3 and CH 3 NH 3 Cl are not stable at low pressure and have higher dissociation vapor pressure than methylammonium sulfate. The observed uptake coefficients of MA on (NH 4 ) 2 SO 4 , NH 4 HSO 4 , NH 4 NO 3 and NH 4 Cl at 298 K were measured to be 6.30±1.03×10 −3 , 1.78±0.36×10 −2 , 8.79±1.99×10 −3 and 2.29±0.28×10 −3 , respectively. A linear free energy relationship was found for the heterogeneous reactions between MA and NH 4 Cl, (NH 4 ) 2 SO 4 and NH 4 NO 3 . Namely, the natural logarithm of uptake coefficients of MA on these ammonium salts is linearly related to the electrostatic potential of the H atom in the NH + 4 group.