Editorial

This special issue consists of several contributions submitted by participants attending the Colloquium on High Resolution Molecular Spectroscopy (HRMS), held in Dijon, France, from 26 to 30 August 2019. This meeting was the 26th in a biennial series of international conferences, which in recent years have taken place alternately in Dijon, France and in another European Country (2009 in Castellammare di Stabia, Italy, 2013 in Budapest, Hungary, and 2017 in Helsinki, Finland, see [1–3]). This series has a long-standing tradition as one of the most important conferences worldwide on all aspects of high-resolution molecular spectroscopy. The next conference will take place in Cologne, Germany, from 29 August to 3 September 2021, and interested scientists should contact Stephan Schlemmer, Cologne, or a member of the executive committee.

With 350 participants, the 2019 HRMS Colloquium had record attendance (see Figure 1). Over the years, the conference has established a special relationship with the journal Molecular Physics, which sponsors the ‘Molecular Physics lecture’ to be given by a most distinguished senior scientist in the field of high-resolution molecular spectroscopy. Previous Molecular Physics lecturers have been Jim K.G. Watson (1997), Alan Carrington (1999), John M. Brown (2001), Richard N. Zare (2003), Terry A. Miller (2005), Fleming F. Crim (2007), Keiichi Tanaka (2009), Marsha I. Lester (2011), Jürgen Troe (2013), Martin Quack (2015) and John L. Hall (2017). For the 2019 meeting, the Molecular Physics lecture was given by Dan Neumark on ‘High resolution photoelectron spectroscopy of negative ions’, see also the paper by J. DeVine et al. in the present issue.

Figure 1. Official conference photograph of the 26th Colloquium of High-Resolution Molecular Spectroscopy held in Dijon, France from 26 to 30 August 2019.

The conference also honours junior scientists by the Amat-Mills Award given for the best contributed papers and by the newly established Jon T. Hougen Travel Award. The laureates of the Amat-Mills Awards, selected by the award committee headed by Agnès Perrin, are Thi Thuy Nguyen (Laboratoire Interuniversitaire des Systèmes Atmosphériques, Université Paris-Est Créteil and Université de Paris) in the category poster and Oliver Zingsheim (University of Cologne) in the category contributed talks. This award consists of a diploma, free registration for the next colloquium and a substantial gift of books, which this year included the Handbook of High Resolution Spectroscopy [4], Fundamentals of Molecular Symmetry [5] and Astronomical Spectroscopy [6]. The first laureates of the Jon T. Hougen Travel Awards, selected by the award committee co-headed by Isabelle Kleiner and Marek Kreglewski, were Rihab Hakiri (University of Tunis) and Aleksei Kuznetsov (University of Tomsk).

Other scientific highlights of the conference included mini-symposia on ‘Environmental far- and mid-IR spectroscopy’, ‘Theoretical predictions of molecular spectra’ and ‘Cold molecules for spectroscopy and dynamics’. Finally, the symposium featured, on the evening of Wednesday 28 August, the scientific lecture ‘The acetylene saga: A journey into HRMS’ by Michel Herman to celebrate the 50th anniversary of the Colloquium. His lecture was preceded by a moving tribute to Dr. Jon T. Hougen: ‘More than 50 years of spectroscopy, motion and matrix elements’ by Isabelle Kleiner, and an entertaining and well-illustrated historical overview entitled ‘1969: The first Dijon HRMS meeting’ by Phil R. Bunker, which described the circumstances that gave birth to the first HRMS meeting held in Dijon in 1969.

The papers presented in this special issue were handled through the normal reviewing and editorial processes. We hope that the tradition of publishing excellent spectroscopic work in Molecular Physics will continue for a long time.