S. Marchetti

Experimental and theoretical investigation of self‐broadening and self‐shifting of ammonia transition lines in the ν2 band

We have measured self‐broadenings and self‐shiftings of several rotovibrational transitions of the ν2 band of NH3. We have found smaller broadenings and bigger shifts with respect to the known data of the inversion spectrum in the microwave region. The experimental results are compared with the Anderson original line broadening theory, successively extended in order to calculate the shift also. The agreement between experiments and theory is quite good so that it is possible to select the right procedure among those usually adopted in order to avoid divergences occurring in the Anderson’s perturbative treatment of the molecular collision matrix.

Self‐broadening and self‐shifting of ammonia lines in the 2ν2 band

We have measured pressure broadening and shifting of some transition lines of ammonia 14NH3 in the 2ν2 band. The agreement between the experimental results and the Anderson theory is satisfactory. We also discuss the possibility of obtaining the value of the dipole moment in the ν2=2 vibrational state from pressure broadening data.

Self‐broadening and self‐shifting of ammonia lines in the 2ν2 band around 16 μm

We have measured the pressure broadening and shift of several transition lines of ammonia, 14NH3, in the 2ν2 band around 16 μm. Satisfactory agreement is found between the experimental results and a slightly modified version of the Anderson theory. A comparison between the theory and measurements of other authors has also been made.

Diode laser spectrum of the ν3 band of 34SF6

Abstract A diode laser was used to measure the absorption spectrum of the ν 3 band of 34 SF 6 . This isotopic species, which is present in the natural sample (4.2%), was cooled in a molecular beam of pure SF 6 . Subbranches up to J = 22 were recorded and identified. The molecular parameters, determined with a simple fitting procedure, are compared with those known of 32 SF 6 and 33 SF 6 .

Diode laser measurements of NH3 absorption lines over the range 931–954 cm−1

Abstract The absorption spectrum of ammonia gas at room temperature in the range 931–954 cm −1 has been measured with a diode laser. Several multiplets have been resolved and almost all the lines have been identified. A rough evaluation of the strength of the absorptions is also given.

Anomalous shape of the IR absorption lines in an expanding molecular beam of ammonia

SummaryThe absorption lines in a free molecular beam possess a width, wider with respect to the Doppler one. Often a two-peak structure is also observed. This effect has been attributed to the angular spreading of the molecular beam and to its condensation. Measurements have been performed on NH3, C2H3C1, CF2Cl2 and SF6 at ∼ 10 μm with a diode laser.

Diode laser spectrum of ammonia around 16 μm

Abstract The absorption spectrum of ammonia over the range 620–634 cm −1 has been investigated with a diode laser. Multiplets have been resolved and almost all the lines, mainly Q -branch transitions of the s 2 ν 2 ← aν 2 band, have been identified.