Excited State Proton Transfer (ESPT) has been studied various spectroscopic methods, such as fluorescence spectrum[1], mass spectrometry (REMPI)[2], decay [3], and so on. However, these methods do not reflect structural change due to PT directly and as a result, inconsistent interpretations have been reported. For example, minimum number of ammonia molecules for ESPT in naphthol/ammonia clusters is proposed from 3 to 5 and has not been established over 25 years. The infrared (IR) �UV double resonance spectroscopy enables us to probe the molecular structure by the vibrational transitions. Particularly hydrogen-bond networks via OH and NH bonds have been extensively studied in 3 micrometer region, however, direct probe of PT has not been succeeded because of spectral broadening of XH bands by strong hydrogen-bond.Here, we would like to report the new possibility to study PT by the mid-IR tunable laser. The mid-IR spectrum (5~10 micrometer) shows skeletal vibrations such as C-O stretching. When PT take place, for example in phenol/naphothol � ammonia clusters, C-O stretching vibration shift to high frequency corresponds to C=O-�H+ vibration. The CO stretchingis free from the broadening effect due to hydrogen-bonding therefore, we can clearly observe the structural change by PT. It has been demonstrated in the study of PT in phenol/ammonia clusters in S0 and minimum numbers of ammonia molecules for complete PT in S0 was revealed to 8 molecules [5]. In this symposium, the mid-IR spectroscopy for ESHT in naphthol/ammonia clusters will also be discussed.[1] O. Cheshnovsky and S. Leutwylar, JCP 1988, 88 , 4127. [2] C. Dedonder-Lardeux et al., PCCP 2001, 3 , 4316. [3] S. K. Kim et al., CPL 1994, 228 , 369. [4] D. C. L�hrs et al., PCCP 2000, 2, 4335. [5] M. Miyazaki et al., JPCA 2013, 117 , 1522.

Mid-infrared spectroscopy for ground and excited state proton transfer in phenol/naphthol-ammonia clusters

248th National Meeting (2014)

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