Electronic Supplementary Material (ESI) for Physical Chemistry Chemical Physics. This journal is © the Owner Societies 2020 Supporting information Specific Counter-cation Effect on the Molecular Orientation of Thiocyanate Anions at the Aqueous Solution Interfaces Hongxing Hao1#, Qing Xie1#,†, Jingwen Ai1, Yuan Wang2, and Hongtao Bian1* 1. Key Laboratory of Applied Surface and Colloid Chemistry, Ministry of Education, School of Chemistry and Chemical Engineering, Shaanxi Normal University, Xi'an, 710119, China 2. Institute of Science and Technology, University of Sanya, Sanya, Hainan, 572022, China # These authors contributed equally to the work. † Current address: Utah State University, 0300 Old Main Hill, Logan, UT 84322, USA. * To whom correspondence should be addressed. Email:
[email protected] (H.B) 1. SFG data and orientation analysis The theoretical data analysis of SFG spectra generated from the air/liquid interface has been described elsewhere.1 The SFG intensity I() can be expressed as a function of the second order susceptibility 2-4 3 2 2 8 sec (2) 2 I() 3 | eff | I(1)I(2 ) (1) c0 n1()n1(1)n1(2 ) Where , , and are the frequencies of the SF signal, visible, and IR laser beam, respectively. n1(i ) is the refractive index of bulk medium i at the frequency of i , I() is the intensity of the SFG signal or the input laser beams, c0 is the speed of light in vacuum, is the incident or reflection angle of the ith light beams from the surface normal, which is defined as the z axis in the laboratory coordinates system (x, y, z), and (2) is the effective macroscopic second-order susceptibility.