Far infrared spectrum of methylamine

Far-Infrared Laser Assignments for Methylamine

“…FIR data are from Ref. [12], except for α in brackets which is calculated from ground-state energies (Ohashi, private communication). Note that the (0,6) E-a wavenumbers are still tentative, as discussed in the text.…”

“…Here, the excited C-N stretching vibrational state will be denoted as "cn". The torsional symmetry σ can be either A or E and the inversion symmetry I can be a or s. We use a signed K for the E levels, with positive K corresponding to levels sometimes labeled as E 1 [12] and negative K corresponding to E 2 . For A symmetry, the levels with K>0 are split by the effects of molecular asymmetry into K-doublets, and we label the components of a resolved K-doublet with a superscript as K + or K -.…”

“…So far, five IR-pump/FIR-laser transition systems have been assigned via closed-loop combination relations employing our new IR data together with previous ground-state FIR observations [12][13][14] and calculated energies (Ohashi, private communication). The combination loops also serve to provide improved frequencies for the FIRL lines to the spectroscopic accuracy.…”

Lamb-dip measurements of ammonia calibration lines in methylamine using a dual-mode CO2-laser-microwave-sideband spectrometer

“…In looking through the other broadband recordings, we noted that the NH 3 features generally appeared with stronger intensities and broader linewidths than the CH 3 NH 2 lines, indicating that the absorption coefficients and pressure broadening parameter are larger for the m 2 band of NH 3 than the CAN stretching band of CH 3 NH 2 . From the broadband scans, 14 strong NH 3 lines could be picked out interspersed through the CH 3 NH 2 spectrum, analogous to the situation in the far-infrared region [10,11] where both NH 3 and H 2 O impurity lines could be identified and used for the CH 3 NH 2 frequency calibration [11]. Here, in order to use the NH 3 lines as accurate position markers for the Doppler-limited CAN stretching spectrum, we switched our spectrometer to the sub-Doppler mode and made precise saturation-dip measurements of the 14 transitions, using 1 kHz source modulation and the 2f second-derivative mode of the digital lock-in amplifier.…”

“…CH 3 NH 2 is a prototype nonrigid molecule with both CH 3 -torsion and NH 2 -wagging large-amplitude motions, producing complex energy structure and dense spectra [3][4][5][6][7][8][9][10][11] that are challenging to analyze in detail. Furthermore, due to chemical exchange with water in the absorption cell, possible slight impurity in the original samples, and even traces in the laboratory air, ammonia lines are generally present in any CH 3 NH 2 spectrum [8][9][10][11], leading to possible confusion in the analysis [9].In this work, using a CO 2 -laser-microwave-sideband spectrometer [12] in its sub-Doppler mode, saturation dips have been resolved and measured precisely for 14 NH 3 lines in the m 2 symmetric bending band that appear in the region of the CAN stretch of CH 3 NH 2 . The commercial CH 3 NH 2 sample supplied by BOC Specialty Gases has a stated purity of 99.5%, so there might be an NH 3 impurity of up to 0.5% given that commercial methylamine is usually prepared by the reaction of ammonia with chloromethane.…”