title: Singlet and doublet states UV-vis spectrum and electronic properties of 3-methylchrysene and 4-methylchrysene in glass matrix.
abstract: The ultraviolet-visual spectrum of 3-methylchrysene, 4-methylchrysene and their radical cations formed by ultraviolet radiations, were measured in glass matrix at the room temperature. In the measured singlet state spectrum we were able to identify the alpha, p, beta, beta' (Clar's) or (1)L(b), (1)L(a)(1)B(b), (1)B(a) (Platt's notation) bands. The presence of alpha, beta or (1)L(b), (1)B(b) was confirmed by calculating their wavelength ratio lambda(alpha)/lambda(beta). Since matrix induces perturbation in the measured spectrum; it becomes necessary to take into account the perturbation while computing the spectrum. An effort has been made in this work to simulate the electronic spectrum in the same environment as is measured. This study presents the first calculated spectrum of these systems and their cations in glass matrix by semi empirical methods. To observe the magnitude of perturbation and hence to see the spectral shift in glass matrix, the spectrum was calculated in the free state as well. Spectral properties such as frontier orbitals gap, dipole moment, mean polarizabilities and its tensors were also computed both in glass matrix and free state using semiemperical method. The measured bands of 3-methylchrysene cation at wavelength 416.50 and 473.85 nm closely match with the available diffuse intersteallar bands (DIBs) at 417.55 and 472.64 nm, respectively. Also the observed 474.85 nm band of 4-methylchrysene cation matches the DIB at 476.00 nm.
authors.affiliation: Physics Section, Department of Applied Sciences and Humanities, Faculty of Engineering and Technology, Jamia Millia Islamia (a Central University), New Delhi 110025, India. mmudassirh@rediffmail.com
authors.forename: Mudassir M
authors.initials: MM
authors.lastname: Husain
authors.forename: H C
authors.initials: HC
authors.lastname: Tandon
authors.forename: Pradeep R
authors.initials: PR
authors.lastname: Varadwaj
mesh_terms: D002412:Cations; D002911:Chrysenes / Q000737:chemistry*; D004583:Electrons; D005898:Glass / Q000737:chemistry*; D008968:Molecular Conformation; D013056:Spectrophotometry, Ultraviolet
chemical_list: D002412:Cations; D002911:Chrysenes; C529617:3-methylchrysene; C529618:4-methylchrysene