[Microscopic raman spectral imaging of oily core].
In the present paper, the authors examined some oily core by Raman spectral imaging methods. Those methods can be classified into two categories, referred to as "parallel or direct imaging" (Imaging) and "series or indirect imaging" (Mapping) techniques. The observed oily core samples which belong to siltstone that was from LONG-HU-PAO structure in SONG-LIAO basin. The samples were made from quartz (approximately 60%), feldspar (approximately 25%) and other impurity, a little recrystallized calcite (approximately 1%) was in the pore, and the argillaceous matter was distributed along the edge of a pore. The experimental work was accomplished using Renishaw MKI2000 Model Raman spectrometer including System 1000 plus filter wheel and filter set. The experimental condition is as follows: room temperature, back-scattering geometry, and excitation wavelength 514. 5 nm (Ar ion laser). In organic matter region, the microscopic Raman spectrum shows that there are two strong scattering peaks at 1 587. 2 and 1334.5 cm(-1), respectively. The former corresponds to intralayer bi-carbon-atomic stretch mode, referred to as "graphite peak"; the latter is disorder-induced feature because of the relaxation of the wave-vector selection rule resulting from finite crystal size effects, referred to as "disorder peak". In pure core substrate region, we observed a sharper peak at 462.7 cm(-1), corresponding to Raman active nonpolar optical mode of quartz crystal. On the basis of the above-mentioned experimental result, we accomplished Raman spectral imaging using mapping (indirect-imaging) procedure and imaging (direct-imaging) procedure, separately. In mapping (indirect-imaging) procedure, although the Raman spectra possess a high spectral resolution (approximately 1 cm(-1)) in every spatial dot, the restructured picture shows a low spatial resolution power (approximately 1 micrometer) because the smallest laser beam radius on the sample plane was restricted by objective lens NA. In imaging (direct-imaging) procedure, the Raman spectra possess a low spectral resolution power (approximately 10-20 cm(-1)), but the picture shows a high spatial resolution power (approximately 0.25-0.30 micrometer) because we need not restructure the picture whose spatial resolution power was only restricted by the optical wavelength. According to the specific structural and spectral properties of sample, and the practical research goal, the authors should select either imaging (direct-imaging) procedure or mapping (indirect-imaging) procedure.
Huang
Qiao-song
QS
College of Physics Science and Technology, China University of Petroleum, Dongying 257061, China. phhqs@163.com
Yu
Zhao-xian
ZX
Li
Jing
J