title: Phase-Specific Raman Analysis ofn-Alkane Melting by Moving-Window Two-Dimensional Correlation Spectroscopy.
abstract: We use moving-window two-dimensional correlation spectroscopy (MW-2DCOS) for phase-specific Raman analysis of then-alkane (C21H44) during melting from the crystalline solid phase to the intermediate rotator phase and to the amorphous molten phase. In MW-2DCOS, individual peak-to-peak correlation analysis within a small subset of spectra provides both temperature-resolved and spectrally disentangled Raman assignments conducive to understanding phase-specific molecular interactions and chain configurations. We demonstrate that autocorrelation MW-2DCOS can determine the phase transition temperatures with a higher resolving power than commonly-used analysis methods including individual peak intensity analysis or principal component analysis. Besides the enhanced temperature resolving power, we demonstrate that asynchronous 2DCOS near the orthorhombic-to-rotator transition temperature can spectrally resolve the two overlapping peaks embedded in the Raman CH2twisting band in the orthorhombic phase, which had been only predicted but not observed due to thermal broadening near the melting temperature.
authors.affiliation: Biosystems & Biomaterials Division, National Institute of Standards and Technology, Gaithersburg, MD 20899, USA.
authors.forename: Ying
authors.initials: Y
authors.lastname: Jin
authors.affiliation: Materials Science & Engineering Division, National Institute of Standards and Technology, Gaithersburg, MD 20899, USA.
authors.forename: Anthony P
authors.initials: AP
authors.lastname: Kotula
authors.affiliation: Physical Measurement Laboratory, National Institute of Standards and Technology, Gaithersburg, MD 20899, USA.
authors.forename: Angela R
authors.initials: AR
authors.lastname: Hight Walker
authors.affiliation: Materials Science & Engineering Division, National Institute of Standards and Technology, Gaithersburg, MD 20899, USA.
authors.forename: Kalman B
authors.initials: KB
authors.lastname: Migler
authors.affiliation: Biosystems & Biomaterials Division, National Institute of Standards and Technology, Gaithersburg, MD 20899, USA.
authors.forename: Young Jong
authors.initials: YJ
authors.lastname: Lee
keywords: Raman spectroscopy; moving-window; n-alkane; phase transition; two-dimensional correlation spectroscopy