Vibrational Cooling Effect of Zeolite on Molecular Desorption Studied by Time-Resolved Laser Desorption Ionization Mass Spectrometry

Jiawei Xu^1,2 and Tatsuya Fujino*^1,2

Received: December 05, 2018;   Published: December 12, 2018

DOI: 10.26717/BJSTR.2018.12.002191

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Abstract

The desorption of the protonated species of 2,4,6-trihydroxyacetophenone (THAP) and 1’-hydroxy-2’-acetonaphthone (HAN) from their crystals was observed by using a time-resolved mass spectrometer and the desorption times were 7.2±2.3 and 14.0±9.4ps, respectively. The desorption time difference was explained by taking into consideration the number of intra- and intermolecular vibrational modes in THAP or HAN dimers. Then, the influence of the three-dimensional framework on the desorption process was investigated. The desorption time for THAP adsorbed on zeolite was 229.1±133ps. As the intermolecular vibrations between THAP and zeolite were directly connected to zeolite lattice vibrations with high density, desorption energy accumulation in those modes became difficult, resulting in the long desorption time. It was clarified that the three-dimensional framework suppressed molecular desorption because it acted as a heat bath, diffusing excess vibrational energy efficiently into its lattice vibrational modes.

Abbreviations : THAP: Trihydroxyacetophenone; LDI: Laser Desorption Ionization; MALDI MS: Matrix Assisted Laser Desorption Ionization Mass Spectrometry; HAN: Hydroxy Acetonaphthone