Pressure broadening measurements confirm the identification of the forbidden ammonia transitionss−3(4, 3) at 887.780 cm−1, Moreover, its pressure shift together with those of submillimeter transitions adds new confidence on the validity of the shift additivity.
The 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.
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 s2ν2 ← aν2 band, have been identified.
A pulsed molecular beam of short duration and high repetition rate has been developed for use in spectroscopic studies and laser application.
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.
With a diode laser we have studied the spectral region around 921 cm−1 of the CF2Cl2 molecule cooled in a free jet. Accurate studies of the intensity of two vibrorotational bands have enabled us to determine their assignment. In addition, the rotational structure has been partially resolved, and approximate fitting parameters have been deduced. The simultaneous use of a diode laser and a free jet has proved to be useful in correctly identifying the origin of the absorption bands.
By using absorption spectra in a pulsed molecular beam, the rotational temperature and the flow density of the jet are deduced. By using this technique, a comparison between a pulsed and a continuous beam is also reported for NH3, CF2Cl2, and C2H3Cl molecular beams. Moreover, the behaviour of the temperature and density inside the pulsed beam is analyzed as a function of time for pure Ammonia. From these measurements, we deduce that a small improvement is obtained for absorption spectroscopy in the jet by using a pulsed molecular beam.
Chemischer InformationsdienstVolume 13, Issue 21 Physical Inorganic Chemistry ChemInform Abstract: DIODE LASER SPECTRUM OF THE ν3 BAND OF SULFUR-34 HEXAFLUORIDE G. BALDACCHINI, G. BALDACCHINISearch for more papers by this authorS. MARCHETTI, S. MARCHETTISearch for more papers by this authorV. MONTELATICI, V. MONTELATICISearch for more papers by this author G. BALDACCHINI, G. BALDACCHINISearch for more papers by this authorS. MARCHETTI, S. MARCHETTISearch for more papers by this authorV. MONTELATICI, V. MONTELATICISearch for more papers by this author First published: May 25, 1982 https://doi.org/10.1002/chin.198221008AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat No abstract is available for this article. Volume13, Issue21May 25, 1982 RelatedInformation
A diode laser was used to measure the absorption spectrum of the ν3 band of 34SF6. This isotopic species, which is present in the natural sample (4.2%), was cooled in a molecular beam of pure SF6. Subbranches up to J = 22 were recorded and identified. The molecular parameters, determined with a simple fitting procedure, are compared with those known of 32SF6 and 33SF6.
The Q-branch transitions of the a2ν2-sν2 band of 14NH3 are analyzed on the basis of a polynomial expansion up to eighth order in J and K. A good fit to the data for J ≤ 11 and precise values of the molecular constants are obtained in a 13-parameter fit (ΔGJJKK = ΔGKKKK = 0). Results of the statistical analysis are used to calculate wavenumbers and variances for transitions with J ≤ 13 that have not yet been measured.
Using a diode laser we have measured infrared absorption of molecular beams of ammonia and freon-12, expanding in a volume evacuated at relatively high pressures (10 −4 -10 −2 bar). The effects of the background gas seem to be negligible. We observed large deviations from a Boltzman rotational energy distribution, as well as the formation of molecular complexes. Rotational temperatures as low as 10 K have been obtained in a beam of freon-12 mixed with helium.
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.
