The interactions of rare gas atoms (Rg 5 Ar, Kr, and Xe) with small neutral and cationic silver clusters have been investigated by density functional methods and the effect of these weak interactions on the resonance Raman spectra of the complexes has been evaluated. The resonance Raman technique that depends on the properties of ground and excited state, seems deeply sensitive to the weak rare gas-metal cluster interactions, and the use of inert gases has been proven to be an excellent approach to recognize the ability of this technique to detect extremely weak interactions. In this work, for Ag 4;6 2Rg, and Ag 1 3;5 2Rg complexes the IR, normal and resonance Raman spectra have been calculated and the effect of rare gas-cluster stretching vibration (v st Ag n 2Rg ) on the pattern and the relative intensities of different spectra have been investigated. The resonance Raman spectra for the weakly interacted complexes (with the interaction energies less than 22.0 kcal/mol) exhibit the v st Ag n 2Rg vibration with the detectable intensity that its intensity increases by going from Ag 6 -Ar to Ag 6 -Xe complex. Moreover, the resonance Raman spectra (based on the excited state gradient approximation) for high intensity nearly degenerate excited states, proved the effect of accumulation of the excited state charge density on the relative intensity of v st Ag n 2Rg vibration.excited-state gradient approximation, metal cluster, resonance Raman, weak interaction
| I N T R O D U C T I O NNoble coinage metal clusters have drawn considerable attention in basic studies and applications due to their particular and novel chemical and physical properties. The unique optical [1][2][3][4][5][6][7][8] and chemical [9][10][11] properties of gold and silver clusters have been investigated for the small sizes up to particles containing several hundreds of atoms with different methods. [12,13] Moreover, controlling and modifying these properties by adjusting size and composition have resulted in a wide range of applications in ultrasensitive chemical and biological sensing. [14][15][16][17] The electronic and structural properties of small metal clusters have been investigated with several spectroscopic methods in the range of electronic and vibrational energies. UV2visible, infrared, and Raman spectroscopy are all powerful tools that have been leveraged for the investigation of metal clusters in the gas phase or embedded in rare gas matrices. [18][19][20][21][22][23][24][25] The rare gas matrix can often provide a chemically inert and an optically transparent medium for the preparation and characterization of small metal clusters. [26,27] Therefore, in several experiments, the rare gas layers were used to weaken the interaction between metal clusters grown or deposited on the surfaces.More recently, the interactions between noble metal and rare gas atom have attracted great interest for theoretical and experimental investigations due to their respective noble characters. The electrostatic charge-transfer interaction and dispersion for...