FTIR and diode laser spectroscopy of isobutylene: Analysis of the rotational structure in the v28 fundamental band

Abstract Rotational structure in the 28 0 1 fundamental band of isobutylene has been examined at room temperature using a combination of FTIR and Pb-salt diode laser instruments. The highest spectral resolution for the FTIR measurements was 0.125 cm−1. Even at this resolution however, rotational structure for the 28 0 1 band could be observed and appeared to possess a very regular pattern. A preliminary spectral assignment was obtained using the Watson/Gora asymptotic approximation for a rigid oblate asymmetric rotor. Within this approximation, the 28 0 1 band origin was determined to be 890.937 (4) cm−1. Excited state rotational constants, without the inclusion of centrifugal distortions terms, are A = 0.3033(16), B = 0.2801(12) and C = 0.15362 (8) cm−1 respectively. Finally, a full set of spectroscopic constants, including quartic centrifugal distortion constants, were obtained for the 28 0 1 band by including the high resolution Pb-salt spectra.

[1]  E. Gora.  An asymptotic method in asymmetric rotor theory , 1965 .

[2]  C. M. Western,et al.  RECENT CHANGES IN PGOPHER: A GENERAL PURPOSE PROGRAM FOR SIMULATING ROTATIONAL STRUCTURE , 2010 .

[3]  D. C. Mckean.  CH stretching frequencies, bond lengths and strengths in acetone, acetaldehyde, propene and isobutene , 1975 .

[4]  H. S. Gutowsky,et al.  Internal rotation and structure of isobutylene , 1991 .

[5]  C. M. Pathak,et al.  Infrared and Raman spectra of isobutene and isobutene-d8 , 1969 .

[6]  Herbert M. Pickett,et al.  The fitting and prediction of vibration-rotation spectra with spin interactions , 1991 .

[7]  Z. Kisiel,et al.  Nuclear quadrupole coupling in Cl2C=CHCl and Cl2C=CH2: Evidence for systematic differences in orientations between internuclear and field gradient axes for terminal quadrupolar nuclei , 1998 .

[8]  V. Laurie.  Studies of internal molecular motions and conformation by microwave spectroscopy , 1970 .

[9]  J. Brown.  Fine structure formation in the electronic spectra of larger molecules , 1969 .

[10]  Walter Gordy,et al.  Microwave Molecular Spectra , 1970 .

[11]  D. Jackson.  High Resolution Spectroscopy , 1947, Nature.

[12]  Z. Kisiel,et al.  The ∠ICI Bending Satellites in the Millimeter-Wave Rotational Spectra of CH2I2 and CD2I2 , 2000 .

[13]  McWhorter,et al.  Intramolecular Vibrational Dynamics of the Asymmetric &dbond;CH2 Hydride Stretch of Isobutene. , 1999, Journal of molecular spectroscopy.

[14]  J. Watson.  Determination of Centrifugal Distortion Coefficients of Asymmetric‐Top Molecules , 1967 .

[15]  J. Watson.  Asymptotic energy levels of a rigid asymmetric top† , 2007 .

[16]  R. Back.  The ultraviolet absorption spectrum of oxalic acid vapor , 1984 .

[17]  V. Laurie.  Microwave Spectrum of Isobutylene. Dipole Moment, Internal Barrier, Equilibrium Conformation, and Structure , 1961 .

[18]  T. Johnson,et al.  Gas-Phase Databases for Quantitative Infrared Spectroscopy , 2004, Applied spectroscopy.

[19]  Mekhtiev,et al.  Contact Transformations and Determinable Parameters in Spectroscopic Fitting Hamiltonians. , 2000, Journal of molecular spectroscopy.