| The microstructure and molecular dynamics information can be obtained through analyzing all kinds of spectra.The spectra are difficult to analyze,as most of the objects that need to be studied are non-ideal systems.The spectra of the species in the system overlapped with each other,and there is usually background signal in the spectra.Therefore,we develop the ratio spectra method to solve the spectral overlapping.In our previous study,we have applied the ratio spectra method to process the Raman spectra.We found a lot of small spectral components which have not been observed before.In this paper,based on the previous studies,we expand the applied range of the ratio spectra method,and we also improve the ratio spectra method.According to the different problems,we offer four different ratio spectra methods.They are relative difference spectra method,Raman ratio spectra method,ratio spectra combine with difference spectra and second order difference spectra method,shift ratio spectra method.Among them,the latter two methods are proposed for the first time.Using the above methods,we specifically solve the following problems:?1?Using Raman ratio spectra method,we obtain the hydration shell Raman spectra that is seriously overlapped with the spectra of bulk water in the ionic aqueous solution.The hydration shell Raman spectra of some kinds of ions at various temperature were record.The isosbestic points are observed in these spectra.The experimental results demonstrated that continuous model can also induce isosbestic points in the spectra.According the molecular dynamics simulation,we explain the isosbestic points in the spectra.In addition,according to Van't Hoff theory,we also obtain the value of enthalpy changes from the bulk water to the hydration shell water of the various ionic aqueous solutions.It is found that the order of these enthalpy changes obey Hofmeister series,this result provide a new direction to study Hofmeister series.?2?Using Ratio spectra combine with difference spectra and second order difference spectra method,we obtain the spectral component which are assigned as the contacted ion pairs[CuCl3?H2O?n]-or[CuCl4?H2O?n]2-from the UV–visible spectra of thin film of CuCl2/H2O solutions.In the ratio spectra and second order difference spectra of thin film of CuCl2/H2O solutions at different concentrations,two new bands at230 and380 nm are obviously observed.The time-dependent density functional theory and the recent theoretical spectra show that the bands are assigned as the contacted ion pairs[CuCl3?H2O?n]-or[CuCl4?H2O?n]2-.Then,we obtain the ratio of the amount of the[CuCl?H2O?n]+and the total amount of[CuCl2?H2O?n]0,[CuCl3?H2O?n]-and[CuCl4?H2O?n]2-at different concentrations by computation.We find that[CuCl?H2O?n]+is the most contacted ion pair in CuCl2/H2O solutions in all the concentration.?3?Using shifted ratio spectra method,we remove the strong fluorescence background signal in the Raman spectra.First,the shifted ratio spectrum was used to judge the position of Raman signal,and then get the fluorescence background spectral regions.Subsequently,according to the subsection linear fitting results,the fluorescence backgrounds are divided into various regions.Then,fluorescent backgrounds are obtained by using a single Gaussian linear to fit the original Raman spectrum in each region.In this way,we can remove the fluorescent background from the original Raman spectra.To prove the correctness and feasibility of this novel method,we use the method to remove the strong fluorescence background in the Raman spectra of low concentration R6G ethanol solution,human plasma,and live mice skin. |
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