In the remaining part of the spectrum of zwitterionic alanine in the gas phase, we identify five modes between 1500-1900 cm -1 . The high energy band at 1900 cm -1 is easily assigned to the asymmetric stretching motion in the fragment CO 2 , as observed in Fig. as well: this is mode 14 represented in Fig. . Centered at 1700 cm -1 , we mainly identify the band corresponding to mode 12 in Fig. : this band is produced by the excitation of the ω5=1425 cm -1 ω6=1441 cm -1 ω8=1465 cm -1 ω7=1467 cm -1 FIG. . Effective modes associated to the spectral region 1350-1500 cm -1 of the IR spectrum of zwitterionic alanine in the gas phase.