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Abstract: In this work we present Windows and Fortran programs which can be used for the Renner–Teller analysis of the vibronic levels of states of linear, triatomic molecules. The programs can do least squares fitting of term values relative to the lowest energy level within a single state, of combination differences between vibronic levels within a single state or of transitions between the levels of two different states. The algorithm allows for the inclusion of Renner–Teller, spin–orbit, vibrational anharmonicity, Fermi resonance and Sears resonance terms in the Hamiltonian matrices. The Windows program RT3, written in Visual Basic 6.0 with a Fortran DLL engine for the numerically intensive computations, facilitates the construction and editing of input files and comparisons of input and output. For very large calculations, the Fortran code may be run as a stand-alone program on mainframe or other computers, but the Windows version offers significant advantages for common usage. Program summary: Title of program: RT3 Catalogue identifier: AEAL_v1_0 Program summary URL: http://cpc.cs.qub.ac.uk/summaries/AEAL_v1_0.html Program obtainable from: CPC Program Library, Queen''s University of Belfast, N. Ireland Licensing provisions: Standard CPC licence, http://cpc.cs.qub.ac.uk/licence/licence.html No. of lines in distributed program, including test data, etc.: 37 477 No. of bytes in distributed program, including test data, etc.: 3 665 414 Distribution format: tar.gz Programming language: Visual Basic 6.0, Fortran 90 Operating systems: Windows 98, Windows XP, Windows Vista, UNIX Classification: 16.2 Nature of problem: The vibronic levels of triatomic molecules in states are complicated by spin–orbit and vibrational-orbital angular momentum coupling (Renner–Teller) effects that make them difficult to assign and analyze. The RT3 program, available in Windows and Fortran versions, can be used to calculate the vibronic energy levels of such systems and fit experimental data to a Hamiltonian that includes Renner–Teller, spin–orbit, vibrational anharmonicity, Fermi resonance and Sears resonance effects. Solution method: The RT3 program solves for the Renner–Teller levels of a state by diagonalizing large truncated Hamiltonian matrices whose elements are generated in a harmonic oscillator basis set. Given an initial input set of constants, the resulting energy levels can be used to least squares fit or predict vibronic term values (relative to the lowest energy level), combination differences between vibronic levels within a electronic state, and transitions between the vibronic levels of two different states. Running time: 6.0 S to run the Transitions.ir3 example file on an Intel Pentium 4 2 GHz CPU with the Windows XP operating system. [Copyright &y& Elsevier]

The first high-resolution infrared spectra of the unstable molecule vinyl alcohol are reported. The spectra have been obtained using a new precursor, 2-chloroethanol, which when pyrolyzed at 1050°C gives strong infrared spectra of vinyl alcohol free of interfering hydrocarbon absorption bands. In this work, we have analyzed the strong ν13fundamental at 817 cm−1and substantially improved the ground state rotational constants by a simultaneous fitting of previous microwave data and a large number of infrared combination differences. The 131upper state was found to be perturbed by the 152“dark” state at 775.7 cm−1, and a complete analysis of the perturbed rotational structure has been achieved using an interacting two-state model. Further small perturbations at high Kaand Jhave been identified as interactions with the ν10and ν12fundamentals at 948 and 960 cm−1, respectively.

The first high-resolution (0.002 cm−1) infrared spectra of the reactive molecule thionylimide, HNSO, are reported. The ν3(NS stretching) and ν5(NSO bending) fundamentals at 1086 and 448 cm−1, respectively, have been analyzed in detail. The ground state rotational constants have been substantially improved by a simultaneous fitting of previously reported microwave data and a large number of infrared combination differences. The excited vibrational state constants of both typeA/Bhybrid bands have been obtained from fitting assignments over a wide range ofJandKavalues. No perturbations were detected in either band.

High-resolution infrared spectra of the out-of-plane bending (ν6) fundamentals of the transient molecules HCOCl and DCOCl are reported. The HCOCl band consists of aC-type component due to the out-of-plane transition moment from the ground state and a Coriolis-induced parallel component which derives its intensity from mixing of the 41and 61vibrational states. In DCOCl, theC-type component is absent, so that all of the band intensity comes from Coriolis-induced borrowing from ν4. The DCOCl ν4and ν6bands have been fitted simultaneously to account for the strong first-order and weaker second-ordera-axis Coriolis interactions between the fundamentals. In HCOCl the ν6band is only weakly perturbed by ν4but is more strongly affected by local interactions with the 52vibrational level, which have been explicitly included in the analysis.Ab initiopredictions of the relative intensities of the ν6fundamentals show that the change in dipole moment is much smaller for DCOCl, accounting for the absence of theC-type component.

A microcomputer-controlled data acquisition and processing system, developed to carry out a variety of pulsed-laser spectroscopic experiments, is described. The hardware consists of largely off-the-shelf spectroscopic instrumentation in conjunction with an IBM personal computer. Versatile software with interactive graphics has been written with the use of Turbo BASIC. The software and hardware components are discussed in detail. As an example of the system performance, the LIF spectrum of S2O has been acquired with the use of an Nd:YAG pumped dye laser as the excitation source. Examples of interactive screen displays and a publication-quality spectrum are presented.

A combination least-squares and band contour analysis of the 210and 220bands of the laser-induced phosphorescence spectrum of theã3B1←X1A1band system silicon difluoride, SiF2, has been completed. Spectra were taken under pyrolysis-jet conditions at a resolution of ca 0.04 cm−1. The rotational (A,B,C), centrifugal distortion (Δk), spin–rotation (a,a0), and spin–spin (α, β) constants for the upper ν2state are reported. An effectiver0structure has been calculated for each upper vibronic state. Some minor intensity anomalies have been observed in the spectra of both bands.