Photoacoustic spectrum of samarium phthalocyanine powder Nibu A. George a, * , R. Jyotsna b , S. Thomas Lee a , B. Aneeshkumar a , Jayan Thomas a , V.P.N. Nampoori a , P. Radhakrishnan a a International School of Photonics, Cochin University of Science and Technology, Cochin 682022, India b Department of Physics, Cochin University of Science and Technology, Cochin 682022, India Received 18 December 2003; accepted 15 May 2004 Available online 15 December 2004 Abstract Photoacoustic spectrum of samarium phthalocyanine powder is recorded and compared with previously reported UV–vis absorption spectra of the same dissolved in different liquid and solid host media. The Davidov splitting of Q band is observed in the PA spectrum but the two bands are overlapped considerably and the shorter wavelength band is more intense and dominating one in the powder spectrum. Ó 2004 Elsevier B.V. All rights reserved. Keywords: Photoacoustics; Phthalocyanine; Absorption spectra 1. Introduction During the past decade phthalocyanines have gained considerable attraction of scientists and technologists owing to their unique optical and electrical properties [1–3]. Not only the easily modifiable structure but also the electronic and morphologic characteristics that are highly favorable for semiconductive or conductive prop- erties have let phthalocyanines in finding a comfortable place among the organic semiconductors. Moreover, superior to many other conducting and semiconducting organic compounds such as charge-transfer complexes, doped poly-acetylene, poly-pyrrole, poly-thiophene andpoly-aniline,metalsubstitutedphthalocyaninespos- sess substantially strong chemical and thermal stability. Optical data storage, gas sensing and electrochromic displays are some among the numerous potential appli- cations of this wonderful compound [4–6]. Phthalocya- nines of rare-earth metals primarily occur in the form of diphthalocyanines with a sandwich type structure and the cation is eightfold coordinated to the two mac- rocycles [7]. One of these phthalocyanine rings is virtu- ally planar while the other is significantly distorted. Among the large number of studies on phthalocyanine compounds reported in the literature, samarium phtha- locyanine (SmPc) is one of the least investigated and exploited member of this family. A recent degenerate four wave mixing study by Unnikrishnan et al. shows that SmPc dissolved in DMF possess a very high third-order susceptibility which makes it a potential candidate in nonlinear optics [8]. In this paper we report the photoacoustic (PA) spec- troscopic studies carried out on SmPc powder. Discov- ered by A.G. Bell more than a century ago, the PA technique is one of the oldest and extensively used mul- tipurpose spectroscopic technique adopted in a vast variety of scientific fields [9,10]. Essentially the PA tech- nique is a closed cavity detection of energy liberated by atoms or molecules through the nonradiative channel, subsequent to the light absorption by a sample. Conse- quently the PA technique has certain unique advantages overconventionalspectroscopicmethodsandisalsofree 0925-3467/$ - see front matter Ó 2004 Elsevier B.V. All rights reserved. doi:10.1016/j.optmat.2004.05.008 * Corresponding author. E-mail address: n.george@chem.rug.nl (N.A. George). www.elsevier.com/locate/optmat Optical Materials 27 (2005) 1593–1595